AbstractClassWithoutAbstractMethod
Since: PMD 3.0
Priority: Medium (3)
The abstract class does not contain any abstract methods. An abstract class suggests an incomplete implementation, which is to be completed by subclasses implementing the abstract methods. If the class is intended to be used as a base class only (not to be instantiated directly) a protected constructor can be provided to prevent direct instantiation.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.AbstractClassWithoutAbstractMethodRule
Example(s):
public abstract class Foo {
void int method1() { ... }
void int method2() { ... }
// consider using abstract methods or removing
// the abstract modifier and adding protected constructors
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/AbstractClassWithoutAbstractMethod" />
AccessorClassGeneration
Since: PMD 1.04
Priority: Medium (3)
Maximum Language Version: Java 10
Instantiation by way of private constructors from outside the constructor’s class often causes the generation of an accessor. A factory method, or non-privatization of the constructor can eliminate this situation. The generated class file is actually an interface. It gives the accessing class the ability to invoke a new hidden package scope constructor that takes the interface as a supplementary parameter. This turns a private constructor effectively into one with package scope, and is challenging to discern.
Note: This rule is only executed for Java 10 or lower. Since Java 11, JEP 181: Nest-Based Access Control has been implemented. This means that in Java 11 and above accessor classes are not generated anymore.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.AccessorClassGenerationRule
Example(s):
public class Outer {
void method(){
Inner ic = new Inner();//Causes generation of accessor class
}
public class Inner {
private Inner(){}
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/AccessorClassGeneration" />
AccessorMethodGeneration
Since: PMD 5.5.4
Priority: Medium (3)
Maximum Language Version: Java 10
When accessing private fields / methods from another class, the Java compiler will generate accessor methods with package-private visibility. This adds overhead, and to the dex method count on Android. This situation can be avoided by changing the visibility of the field / method from private to package-private.
Note: This rule is only executed for Java 10 or lower. Since Java 11, JEP 181: Nest-Based Access Control has been implemented. This means that in Java 11 and above accessor classes are not generated anymore.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.AccessorMethodGenerationRule
Example(s):
public class OuterClass {
private int counter;
/* package */ int id;
public class InnerClass {
InnerClass() {
OuterClass.this.counter++; // wrong accessor method will be generated
}
public int getOuterClassId() {
return OuterClass.this.id; // id is package-private, no accessor method needed
}
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/AccessorMethodGeneration" />
ArrayIsStoredDirectly
Since: PMD 2.2
Priority: Medium (3)
Constructors and methods receiving arrays should clone objects and store the copy. This prevents future changes from the user from affecting the original array.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.ArrayIsStoredDirectlyRule
Example(s):
public class Foo {
private String [] x;
public void foo (String [] param) {
// Don't do this, make a copy of the array at least
this.x=param;
}
}
This rule has the following properties:
Name | Default Value | Description | Multivalued |
---|---|---|---|
allowPrivate | true | If true, allow private methods/constructors to store arrays directly | no |
Use this rule with the default properties by just referencing it:
<rule ref="category/java/bestpractices.xml/ArrayIsStoredDirectly" />
Use this rule and customize it:
<rule ref="category/java/bestpractices.xml/ArrayIsStoredDirectly">
<properties>
<property name="allowPrivate" value="true" />
</properties>
</rule>
AvoidMessageDigestField
Since: PMD 6.18.0
Priority: Medium (3)
Declaring a MessageDigest instance as a field make this instance directly available to multiple threads. Such sharing of MessageDigest instances should be avoided if possible since it leads to wrong results if the access is not synchronized correctly. Just create a new instance and use it locally, where you need it. Creating a new instance is easier than synchronizing access to a shared instance.
This rule is defined by the following XPath expression:
//FieldDeclaration[pmd-java:typeIs('java.security.MessageDigest')]
Example(s):
import java.security.MessageDigest;
public class AvoidMessageDigestFieldExample {
private final MessageDigest sharedMd;
public AvoidMessageDigestFieldExample() throws Exception {
sharedMd = MessageDigest.getInstance("SHA-256");
}
public byte[] calculateHashShared(byte[] data) {
// sharing a MessageDigest like this without synchronizing access
// might lead to wrong results
sharedMd.reset();
sharedMd.update(data);
return sharedMd.digest();
}
// better
public byte[] calculateHash(byte[] data) throws Exception {
MessageDigest md = MessageDigest.getInstance("SHA-256");
md.update(data);
return md.digest();
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/AvoidMessageDigestField" />
AvoidPrintStackTrace
Since: PMD 3.2
Priority: Medium (3)
Avoid printStackTrace(); use a logger call instead.
This rule is defined by the following XPath expression:
//PrimaryExpression[
( PrimaryPrefix[Name[contains(@Image,'printStackTrace')]]
| PrimarySuffix[@Image='printStackTrace']
)/following-sibling::*[1][self::PrimarySuffix/Arguments[@Size=0]]
]
Example(s):
class Foo {
void bar() {
try {
// do something
} catch (Exception e) {
e.printStackTrace();
}
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/AvoidPrintStackTrace" />
AvoidReassigningCatchVariables
Since: PMD 6.27.0
Priority: Medium (3)
Reassigning exception variables caught in a catch statement should be avoided because of:
1) If it is needed, multi catch can be easily added and code will still compile.
2) Following the principle of least surprise we want to make sure that a variable caught in a catch statement is always the one thrown in a try block.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.AvoidReassigningCatchVariablesRule
Example(s):
public class Foo {
public void foo() {
try {
// do something
} catch (Exception e) {
e = new NullPointerException(); // not recommended
}
try {
// do something
} catch (MyException | ServerException e) {
e = new RuntimeException(); // won't compile
}
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/AvoidReassigningCatchVariables" />
AvoidReassigningLoopVariables
Since: PMD 6.11.0
Priority: Medium (3)
Reassigning loop variables can lead to hard-to-find bugs. Prevent or limit how these variables can be changed.
In foreach-loops, configured by the foreachReassign
property:
deny
: Report any reassignment of the loop variable in the loop body. This is the default.allow
: Don’t check the loop variable.firstOnly
: Report any reassignments of the loop variable, except as the first statement in the loop body. This is useful if some kind of normalization or clean-up of the value before using is permitted, but any other change of the variable is not.
In for-loops, configured by the forReassign
property:
deny
: Report any reassignment of the control variable in the loop body. This is the default.allow
: Don’t check the control variable.skip
: Report any reassignments of the control variable, except conditional increments/decrements (++
,--
,+=
,-=
). This prevents accidental reassignments or unconditional increments of the control variable.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.AvoidReassigningLoopVariablesRule
Example(s):
public class Foo {
private void foo() {
for (String s : listOfStrings()) {
s = s.trim(); // OK, when foreachReassign is "firstOnly" or "allow"
doSomethingWith(s);
s = s.toUpper(); // OK, when foreachReassign is "allow"
doSomethingElseWith(s);
}
for (int i=0; i < 10; i++) {
if (check(i)) {
i++; // OK, when forReassign is "skip" or "allow"
}
i = 5; // OK, when forReassign is "allow"
doSomethingWith(i);
}
}
}
This rule has the following properties:
Name | Default Value | Description | Multivalued |
---|---|---|---|
foreachReassign | deny | how/if foreach control variables may be reassigned | no |
forReassign | deny | how/if for control variables may be reassigned | no |
Use this rule with the default properties by just referencing it:
<rule ref="category/java/bestpractices.xml/AvoidReassigningLoopVariables" />
Use this rule and customize it:
<rule ref="category/java/bestpractices.xml/AvoidReassigningLoopVariables">
<properties>
<property name="foreachReassign" value="deny" />
<property name="forReassign" value="deny" />
</properties>
</rule>
AvoidReassigningParameters
Since: PMD 1.0
Priority: Medium High (2)
Reassigning values to incoming parameters of a method or constructor is not recommended, as this can make the code more difficult to understand. The code is often read with the assumption that parameter values don’t change and an assignment violates therefore the principle of least astonishment. This is especially a problem if the parameter is documented e.g. in the method’s javadoc and the new content differs from the original documented content.
Use temporary local variables instead. This allows you to assign a new name, which makes the code better understandable.
Note that this rule considers both methods and constructors. If there are multiple assignments for a formal parameter, then only the first assignment is reported.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.AvoidReassigningParametersRule
Example(s):
public class Hello {
private void greet(String name) {
name = name.trim();
System.out.println("Hello " + name);
// preferred
String trimmedName = name.trim();
System.out.println("Hello " + trimmedName);
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/AvoidReassigningParameters" />
AvoidStringBufferField
Since: PMD 4.2
Priority: Medium (3)
StringBuffers/StringBuilders can grow considerably, and so may become a source of memory leaks if held within objects with long lifetimes.
This rule is defined by the following XPath expression:
//FieldDeclaration/Type/ReferenceType/ClassOrInterfaceType[@Image = 'StringBuffer' or @Image = 'StringBuilder']
Example(s):
public class Foo {
private StringBuffer buffer; // potential memory leak as an instance variable;
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/AvoidStringBufferField" />
AvoidUsingHardCodedIP
Since: PMD 4.1
Priority: Medium (3)
Application with hard-coded IP addresses can become impossible to deploy in some cases. Externalizing IP adresses is preferable.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.AvoidUsingHardCodedIPRule
Example(s):
public class Foo {
private String ip = "127.0.0.1"; // not recommended
}
This rule has the following properties:
Name | Default Value | Description | Multivalued |
---|---|---|---|
checkAddressTypes | IPv4 mapped IPv6 | IPv6 | IPv4 | Check for IP address types. | yes. Delimiter is ‘|’. |
Use this rule with the default properties by just referencing it:
<rule ref="category/java/bestpractices.xml/AvoidUsingHardCodedIP" />
Use this rule and customize it:
<rule ref="category/java/bestpractices.xml/AvoidUsingHardCodedIP">
<properties>
<property name="checkAddressTypes" value="IPv4 mapped IPv6|IPv6|IPv4" />
</properties>
</rule>
CheckResultSet
Since: PMD 4.1
Priority: Medium (3)
Always check the return values of navigation methods (next, previous, first, last) of a ResultSet. If the value return is ‘false’, it should be handled properly.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.CheckResultSetRule
Example(s):
Statement stat = conn.createStatement();
ResultSet rst = stat.executeQuery("SELECT name FROM person");
rst.next(); // what if it returns false? bad form
String firstName = rst.getString(1);
Statement stat = conn.createStatement();
ResultSet rst = stat.executeQuery("SELECT name FROM person");
if (rst.next()) { // result is properly examined and used
String firstName = rst.getString(1);
} else {
// handle missing data
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/CheckResultSet" />
ConstantsInInterface
Since: PMD 5.5
Priority: Medium (3)
Avoid constants in interfaces. Interfaces should define types, constants are implementation details better placed in classes or enums. See Effective Java, item 19.
This rule is defined by the following XPath expression:
//ClassOrInterfaceDeclaration[@Interface= true()][$ignoreIfHasMethods= false() or not(.//MethodDeclaration)]//FieldDeclaration
Example(s):
public interface ConstantInterface {
public static final int CONST1 = 1; // violation, no fields allowed in interface!
static final int CONST2 = 1; // violation, no fields allowed in interface!
final int CONST3 = 1; // violation, no fields allowed in interface!
int CONST4 = 1; // violation, no fields allowed in interface!
}
// with ignoreIfHasMethods = false
public interface AnotherConstantInterface {
public static final int CONST1 = 1; // violation, no fields allowed in interface!
int anyMethod();
}
// with ignoreIfHasMethods = true
public interface YetAnotherConstantInterface {
public static final int CONST1 = 1; // no violation
int anyMethod();
}
This rule has the following properties:
Name | Default Value | Description | Multivalued |
---|---|---|---|
ignoreIfHasMethods | true | Whether to ignore constants in interfaces if the interface defines any methods | no |
Use this rule with the default properties by just referencing it:
<rule ref="category/java/bestpractices.xml/ConstantsInInterface" />
Use this rule and customize it:
<rule ref="category/java/bestpractices.xml/ConstantsInInterface">
<properties>
<property name="ignoreIfHasMethods" value="true" />
</properties>
</rule>
DefaultLabelNotLastInSwitchStmt
Since: PMD 1.5
Priority: Medium (3)
By convention, the default label should be the last label in a switch statement.
This rule is defined by the following XPath expression:
//SwitchStatement
[not(SwitchLabel[position() = last()][@Default= true()])]
[SwitchLabel[@Default= true()]]
Example(s):
public class Foo {
void bar(int a) {
switch (a) {
case 1: // do something
break;
default: // the default case should be last, by convention
break;
case 2:
break;
}
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/DefaultLabelNotLastInSwitchStmt" />
DoubleBraceInitialization
Since: PMD 6.16.0
Priority: Medium (3)
Double brace initialisation is a pattern to initialise eg collections concisely. But it implicitly generates a new .class file, and the object holds a strong reference to the enclosing object. For those reasons, it is preferable to initialize the object normally, even though it’s verbose.
This rule counts any anonymous class which only has a single initializer as an instance of double-brace initialization. There is currently no way to find out whether a method called in the initializer is not accessible from outside the anonymous class, and those legit cases should be suppressed for the time being.
This rule is defined by the following XPath expression:
//AllocationExpression/ClassOrInterfaceBody[count(*)=1]/*/Initializer[@Static=false()]
Example(s):
// this is double-brace initialization
return new ArrayList<String>(){{
add("a");
add("b");
add("c");
}};
// the better way is to not create an anonymous class:
List<String> a = new ArrayList<>();
a.add("a");
a.add("b");
a.add("c");
return a;
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/DoubleBraceInitialization" />
ForLoopCanBeForeach
Since: PMD 6.0.0
Priority: Medium (3)
Minimum Language Version: Java 1.5
Reports loops that can be safely replaced with the foreach syntax. The rule considers loops over lists, arrays and iterators. A loop is safe to replace if it only uses the index variable to access an element of the list or array, only has one update statement, and loops through every element of the list or array left to right.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.ForLoopCanBeForeachRule
Example(s):
public class MyClass {
void loop(List<String> l) {
for (int i = 0; i < l.size(); i++) { // pre Java 1.5
System.out.println(l.get(i));
}
for (String s : l) { // post Java 1.5
System.out.println(s);
}
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/ForLoopCanBeForeach" />
ForLoopVariableCount
Since: PMD 6.11.0
Priority: Medium (3)
Having a lot of control variables in a ‘for’ loop makes it harder to see what range of values the loop iterates over. By default this rule allows a regular ‘for’ loop with only one variable.
This rule is defined by the following XPath expression:
//ForInit/LocalVariableDeclaration[count(VariableDeclarator) > $maximumVariables]
Example(s):
// this will be reported with the default setting of at most one control variable in a for loop
for (int i = 0, j = 0; i < 10; i++, j += 2) {
foo();
This rule has the following properties:
Name | Default Value | Description | Multivalued |
---|---|---|---|
maximumVariables | 1 | A regular for statement will have 1 control variable | no |
Use this rule with the default properties by just referencing it:
<rule ref="category/java/bestpractices.xml/ForLoopVariableCount" />
Use this rule and customize it:
<rule ref="category/java/bestpractices.xml/ForLoopVariableCount">
<properties>
<property name="maximumVariables" value="1" />
</properties>
</rule>
GuardLogStatement
Since: PMD 5.1.0
Priority: Medium High (2)
Whenever using a log level, one should check if the loglevel is actually enabled, or otherwise skip the associate String creation and manipulation.
An alternative to checking the log level are substituting parameters, formatters or lazy logging with lambdas. The available alternatives depend on the actual logging framework.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.GuardLogStatementRule
Example(s):
// Add this for performance
if (log.isDebugEnabled()) {
log.debug("log something" + param1 + " and " + param2 + "concat strings");
}
// Avoid the guarding if statement with substituting parameters
log.debug("log something {} and {}", param1, param2);
// Avoid the guarding if statement with formatters
log.debug("log something %s and %s", param1, param2);
// Avoid the guarding if statement with lazy logging and lambdas
log.debug("log something expensive: {}", () -> calculateExpensiveLoggingText());
This rule has the following properties:
Name | Default Value | Description | Multivalued |
---|---|---|---|
logLevels | trace , debug , info , warn , error , log , finest , finer , fine , info , warning , severe | LogLevels to guard | yes. Delimiter is ‘,’. |
guardsMethods | isTraceEnabled , isDebugEnabled , isInfoEnabled , isWarnEnabled , isErrorEnabled , isLoggable | Method use to guard the log statement | yes. Delimiter is ‘,’. |
Use this rule with the default properties by just referencing it:
<rule ref="category/java/bestpractices.xml/GuardLogStatement" />
Use this rule and customize it:
<rule ref="category/java/bestpractices.xml/GuardLogStatement">
<properties>
<property name="logLevels" value="trace,debug,info,warn,error,log,finest,finer,fine,info,warning,severe" />
<property name="guardsMethods" value="isTraceEnabled,isDebugEnabled,isInfoEnabled,isWarnEnabled,isErrorEnabled,isLoggable" />
</properties>
</rule>
JUnit4SuitesShouldUseSuiteAnnotation
Since: PMD 4.0
Priority: Medium (3)
In JUnit 3, test suites are indicated by the suite() method. In JUnit 4, suites are indicated through the @RunWith(Suite.class) annotation.
This rule is defined by the following XPath expression:
//ClassOrInterfaceBodyDeclaration
[MethodDeclaration[@Name='suite']/ResultType/Type/ReferenceType/ClassOrInterfaceType[pmd-java:typeIs('junit.framework.Test')]]
[not(MethodDeclaration/Block/BlockStatement/Statement/ReturnStatement//ClassOrInterfaceType[pmd-java:typeIs('junit.framework.JUnit4TestAdapter')])]
Example(s):
public class BadExample extends TestCase{
public static Test suite(){
return new Suite();
}
}
@RunWith(Suite.class)
@SuiteClasses( { TestOne.class, TestTwo.class })
public class GoodTest {
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/JUnit4SuitesShouldUseSuiteAnnotation" />
JUnit4TestShouldUseAfterAnnotation
Since: PMD 4.0
Priority: Medium (3)
In JUnit 3, the tearDown method was used to clean up all data entities required in running tests. JUnit 4 skips the tearDown method and executes all methods annotated with @After after running each test. JUnit 5 introduced @AfterEach and @AfterAll annotations to execute methods after each test or after all tests in the class, respectively.
This rule is defined by the following XPath expression:
//ClassOrInterfaceBodyDeclaration
[MethodDeclaration[@Name='tearDown']]
[not(Annotation/*/Name[
pmd-java:typeIs('org.junit.After')
or pmd-java:typeIs('org.junit.jupiter.api.AfterEach')
or pmd-java:typeIs('org.junit.jupiter.api.AfterAll')
or pmd-java:typeIs('org.testng.annotations.AfterMethod')])]
Example(s):
public class MyTest {
public void tearDown() {
bad();
}
}
public class MyTest2 {
@After public void tearDown() {
good();
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/JUnit4TestShouldUseAfterAnnotation" />
JUnit4TestShouldUseBeforeAnnotation
Since: PMD 4.0
Priority: Medium (3)
In JUnit 3, the setUp method was used to set up all data entities required in running tests. JUnit 4 skips the setUp method and executes all methods annotated with @Before before all tests. JUnit 5 introduced @BeforeEach and @BeforeAll annotations to execute methods before each test or before all tests in the class, respectively.
This rule is defined by the following XPath expression:
//ClassOrInterfaceBodyDeclaration
[MethodDeclaration[@Name='setUp']]
[not(Annotation/*/Name[
pmd-java:typeIs('org.junit.Before')
or pmd-java:typeIs('org.junit.jupiter.api.BeforeEach')
or pmd-java:typeIs('org.junit.jupiter.api.BeforeAll')
or pmd-java:typeIs('org.testng.annotations.BeforeMethod')])]
Example(s):
public class MyTest {
public void setUp() {
bad();
}
}
public class MyTest2 {
@Before public void setUp() {
good();
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/JUnit4TestShouldUseBeforeAnnotation" />
JUnit4TestShouldUseTestAnnotation
Since: PMD 4.0
Priority: Medium (3)
In JUnit 3, the framework executed all methods which started with the word test as a unit test. In JUnit 4, only methods annotated with the @Test annotation are executed. In JUnit 5, one of the following annotations should be used for tests: @Test, @RepeatedTest, @TestFactory, @TestTemplate or @ParameterizedTest.
This rule is defined by the following XPath expression:
//ClassOrInterfaceDeclaration[
matches(@SimpleName, $testClassPattern)
or ExtendsList/ClassOrInterfaceType[pmd-java:typeIs('junit.framework.TestCase')]]
/ClassOrInterfaceBody/ClassOrInterfaceBodyDeclaration[MethodDeclaration[@Public=true() and starts-with(@Name, 'test')]]
[not(Annotation//Name[
pmd-java:typeIs('org.junit.Test')
or pmd-java:typeIs('org.junit.jupiter.api.Test') or pmd-java:typeIs('org.junit.jupiter.api.RepeatedTest')
or pmd-java:typeIs('org.junit.jupiter.api.TestFactory') or pmd-java:typeIs('org.junit.jupiter.api.TestTemplate')
or pmd-java:typeIs('org.junit.jupiter.params.ParameterizedTest')
])]
Example(s):
public class MyTest {
public void testBad() {
doSomething();
}
@Test
public void testGood() {
doSomething();
}
}
This rule has the following properties:
Name | Default Value | Description | Multivalued |
---|---|---|---|
testClassPattern | Test | The regex pattern used to identify test classes | no |
Use this rule with the default properties by just referencing it:
<rule ref="category/java/bestpractices.xml/JUnit4TestShouldUseTestAnnotation" />
Use this rule and customize it:
<rule ref="category/java/bestpractices.xml/JUnit4TestShouldUseTestAnnotation">
<properties>
<property name="testClassPattern" value="Test" />
</properties>
</rule>
JUnit5TestShouldBePackagePrivate
Since: PMD 6.35.0
Priority: Medium (3)
Reports JUnit 5 test classes and methods that are not package-private. Contrary to JUnit 4 tests, which required public visibility to be run by the engine, JUnit 5 tests can also be run if they’re package-private. Marking them as such is a good practice to limit their visibility.
Test methods are identified as those which use @Test
, @RepeatedTest
,
@TestFactory
, @TestTemplate
or @ParameterizedTest
.
This rule is defined by the following XPath expression:
//ClassOrInterfaceDeclaration[
(: a Junit 5 test class, ie, it has methods with the annotation :)
@Interface=false() and
ClassOrInterfaceBody/ClassOrInterfaceBodyDeclaration
[Annotation//Name[
pmd-java:typeIs('org.junit.jupiter.api.Test') or pmd-java:typeIs('org.junit.jupiter.api.RepeatedTest')
or pmd-java:typeIs('org.junit.jupiter.api.TestFactory') or pmd-java:typeIs('org.junit.jupiter.api.TestTemplate')
or pmd-java:typeIs('org.junit.jupiter.params.ParameterizedTest')
]]
[MethodDeclaration]
]/(
self::*[@Abstract=false() and (@Public=true() or @Protected=true())]
| ClassOrInterfaceBody/ClassOrInterfaceBodyDeclaration
[Annotation//Name[
pmd-java:typeIs('org.junit.jupiter.api.Test') or pmd-java:typeIs('org.junit.jupiter.api.RepeatedTest')
or pmd-java:typeIs('org.junit.jupiter.api.TestFactory') or pmd-java:typeIs('org.junit.jupiter.api.TestTemplate')
or pmd-java:typeIs('org.junit.jupiter.params.ParameterizedTest')
]]
/MethodDeclaration[@Public=true() or @Protected=true()]
)
Example(s):
class MyTest { // not public, that's fine
@Test
public void testBad() { } // should not have a public modifier
@Test
protected void testAlsoBad() { } // should not have a protected modifier
@Test
private void testNoRun() { } // should not have a private modifier
@Test
void testGood() { } // package private as expected
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/JUnit5TestShouldBePackagePrivate" />
JUnitAssertionsShouldIncludeMessage
Since: PMD 1.04
Priority: Medium (3)
JUnit assertions should include an informative message - i.e., use the three-argument version of assertEquals(), not the two-argument version.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.JUnitAssertionsShouldIncludeMessageRule
Example(s):
public class Foo extends TestCase {
public void testSomething() {
assertEquals("foo", "bar");
// Use the form:
// assertEquals("Foo does not equals bar", "foo", "bar");
// instead
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/JUnitAssertionsShouldIncludeMessage" />
JUnitTestContainsTooManyAsserts
Since: PMD 5.0
Priority: Medium (3)
Unit tests should not contain too many asserts. Many asserts are indicative of a complex test, for which it is harder to verify correctness. Consider breaking the test scenario into multiple, shorter test scenarios. Customize the maximum number of assertions used by this Rule to suit your needs.
This rule checks for JUnit4, JUnit5 and TestNG Tests, as well as methods starting with "test".
This rule is defined by the following XPath expression:
//MethodDeclaration[@Name[matches(.,'^test')] or ../Annotation/MarkerAnnotation/Name[
pmd-java:typeIs('org.junit.Test')
or pmd-java:typeIs('org.junit.jupiter.api.Test')
or pmd-java:typeIs('org.junit.jupiter.api.RepeatedTest')
or pmd-java:typeIs('org.junit.jupiter.api.TestFactory')
or pmd-java:typeIs('org.junit.jupiter.api.TestTemplate')
or pmd-java:typeIs('org.junit.jupiter.params.ParameterizedTest')
or pmd-java:typeIs('org.testng.annotations.Test')
]]
[count(.//PrimaryPrefix/Name[@Image[matches(.,'^assert')]]) > $maximumAsserts]
Example(s):
public class MyTestCase extends TestCase {
// Ok
public void testMyCaseWithOneAssert() {
boolean myVar = false;
assertFalse("should be false", myVar);
}
// Bad, too many asserts (assuming max=1)
public void testMyCaseWithMoreAsserts() {
boolean myVar = false;
assertFalse("myVar should be false", myVar);
assertEquals("should equals false", false, myVar);
}
}
This rule has the following properties:
Name | Default Value | Description | Multivalued |
---|---|---|---|
maximumAsserts | 1 | Maximum number of Asserts in a test method | no |
Use this rule with the default properties by just referencing it:
<rule ref="category/java/bestpractices.xml/JUnitTestContainsTooManyAsserts" />
Use this rule and customize it:
<rule ref="category/java/bestpractices.xml/JUnitTestContainsTooManyAsserts">
<properties>
<property name="maximumAsserts" value="1" />
</properties>
</rule>
JUnitTestsShouldIncludeAssert
Since: PMD 2.0
Priority: Medium (3)
JUnit tests should include at least one assertion. This makes the tests more robust, and using assert with messages provide the developer a clearer idea of what the test does.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.JUnitTestsShouldIncludeAssertRule
Example(s):
public class Foo extends TestCase {
public void testSomething() {
Bar b = findBar();
// This is better than having a NullPointerException
// assertNotNull("bar not found", b);
b.work();
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/JUnitTestsShouldIncludeAssert" />
JUnitUseExpected
Since: PMD 4.0
Priority: Medium (3)
In JUnit4, use the @Test(expected) annotation to denote tests that should throw exceptions.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.JUnitUseExpectedRule
Example(s):
public class MyTest {
@Test
public void testBad() {
try {
doSomething();
fail("should have thrown an exception");
} catch (Exception e) {
}
}
@Test(expected=Exception.class)
public void testGood() {
doSomething();
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/JUnitUseExpected" />
LiteralsFirstInComparisons
Since: PMD 6.24.0
Priority: Medium (3)
Position literals first in all String comparisons, if the second argument is null then NullPointerExceptions can be avoided, they will just return false. Note that switching literal positions for compareTo and compareToIgnoreCase may change the result, see examples.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.LiteralsFirstInComparisonsRule
Example(s):
class Foo {
boolean bar(String x) {
return x.equals("2"); // should be "2".equals(x)
}
boolean bar(String x) {
return x.equalsIgnoreCase("2"); // should be "2".equalsIgnoreCase(x)
}
boolean bar(String x) {
return (x.compareTo("bar") > 0); // should be: "bar".compareTo(x) < 0
}
boolean bar(String x) {
return (x.compareToIgnoreCase("bar") > 0); // should be: "bar".compareToIgnoreCase(x) < 0
}
boolean bar(String x) {
return x.contentEquals("bar"); // should be "bar".contentEquals(x)
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/LiteralsFirstInComparisons" />
LooseCoupling
Since: PMD 0.7
Priority: Medium (3)
The use of implementation types (i.e., HashSet) as object references limits your ability to use alternate implementations in the future as requirements change. Whenever available, referencing objects by their interface types (i.e, Set) provides much more flexibility.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.LooseCouplingRule
Example(s):
import java.util.ArrayList;
import java.util.HashSet;
public class Bar {
// sub-optimal approach
private ArrayList<SomeType> list = new ArrayList<>();
public HashSet<SomeType> getFoo() {
return new HashSet<SomeType>();
}
// preferred approach
private List<SomeType> list = new ArrayList<>();
public Set<SomeType> getFoo() {
return new HashSet<SomeType>();
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/LooseCoupling" />
MethodReturnsInternalArray
Since: PMD 2.2
Priority: Medium (3)
Exposing internal arrays to the caller violates object encapsulation since elements can be removed or replaced outside of the object that owns it. It is safer to return a copy of the array.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.MethodReturnsInternalArrayRule
Example(s):
public class SecureSystem {
UserData [] ud;
public UserData [] getUserData() {
// Don't return directly the internal array, return a copy
return ud;
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/MethodReturnsInternalArray" />
MissingOverride
Since: PMD 6.2.0
Priority: Medium (3)
Minimum Language Version: Java 1.5
Annotating overridden methods with @Override ensures at compile time that the method really overrides one, which helps refactoring and clarifies intent.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.MissingOverrideRule
Example(s):
public class Foo implements Runnable {
// This method is overridden, and should have an @Override annotation
public void run() {
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/MissingOverride" />
OneDeclarationPerLine
Since: PMD 5.0
Priority: Medium Low (4)
Java allows the use of several variables declaration of the same type on one line. However, it can lead to quite messy code. This rule looks for several declarations on the same line.
This rule is defined by the following XPath expression:
//LocalVariableDeclaration
[not(parent::ForInit)]
[count(VariableDeclarator) > 1]
[$strictMode or count(distinct-values(VariableDeclarator/@BeginLine)) != count(VariableDeclarator)]
|
//FieldDeclaration
[count(VariableDeclarator) > 1]
[$strictMode or count(distinct-values(VariableDeclarator/@BeginLine)) != count(VariableDeclarator)]
Example(s):
String name; // separate declarations
String lastname;
String name, lastname; // combined declaration, a violation
String name,
lastname; // combined declaration on multiple lines, no violation by default.
// Set property strictMode to true to mark this as violation.
This rule has the following properties:
Name | Default Value | Description | Multivalued |
---|---|---|---|
strictMode | false | If true, mark combined declaration even if the declarations are on separate lines. | no |
Use this rule with the default properties by just referencing it:
<rule ref="category/java/bestpractices.xml/OneDeclarationPerLine" />
Use this rule and customize it:
<rule ref="category/java/bestpractices.xml/OneDeclarationPerLine">
<properties>
<property name="strictMode" value="false" />
</properties>
</rule>
PositionLiteralsFirstInCaseInsensitiveComparisons
Deprecated
Since: PMD 5.1
Priority: Medium (3)
Position literals first in comparisons, if the second argument is null then NullPointerExceptions can be avoided, they will just return false.
Note: This rule is deprecated since PMD 6.24.0 and will be removed with PMD 7.0.0. The rule is replaced
by the more general rule LiteralsFirstInComparisons
.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.PositionLiteralsFirstInCaseInsensitiveComparisonsRule
Example(s):
class Foo {
boolean bar(String x) {
return x.equalsIgnoreCase("2"); // should be "2".equalsIgnoreCase(x)
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/PositionLiteralsFirstInCaseInsensitiveComparisons" />
PositionLiteralsFirstInComparisons
Deprecated
Since: PMD 3.3
Priority: Medium (3)
Position literals first in comparisons, if the second argument is null then NullPointerExceptions can be avoided, they will just return false.
Note: This rule is deprecated since PMD 6.24.0 and will be removed with PMD 7.0.0. The rule is replaced
by the more general rule LiteralsFirstInComparisons
.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.PositionLiteralsFirstInComparisonsRule
Example(s):
class Foo {
boolean bar(String x) {
return x.equals("2"); // should be "2".equals(x)
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/PositionLiteralsFirstInComparisons" />
PreserveStackTrace
Since: PMD 3.7
Priority: Medium (3)
Throwing a new exception from a catch block without passing the original exception into the new exception will cause the original stack trace to be lost making it difficult to debug effectively.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.PreserveStackTraceRule
Example(s):
public class Foo {
void good() {
try{
Integer.parseInt("a");
} catch (Exception e) {
throw new Exception(e); // first possibility to create exception chain
}
try {
Integer.parseInt("a");
} catch (Exception e) {
throw (IllegalStateException)new IllegalStateException().initCause(e); // second possibility to create exception chain.
}
}
void bad() {
try{
Integer.parseInt("a");
} catch (Exception e) {
throw new Exception(e.getMessage());
}
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/PreserveStackTrace" />
PrimitiveWrapperInstantiation
Since: PMD 6.37.0
Priority: Medium (3)
Reports usages of primitive wrapper constructors. They are deprecated
since Java 9 and should not be used. Even before Java 9, they can
be replaced with usage of the corresponding static valueOf
factory method
(which may be automatically inserted by the compiler since Java 1.5).
This has the advantage that it may reuse common instances instead of creating
a new instance each time.
Note that for Boolean
, the named constants Boolean.TRUE
and Boolean.FALSE
are preferred instead of Boolean.valueOf
.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.PrimitiveWrapperInstantiationRule
Example(s):
public class Foo {
private Integer ZERO = new Integer(0); // violation
private Integer ZERO1 = Integer.valueOf(0); // better
private Integer ZERO1 = 0; // even better
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/PrimitiveWrapperInstantiation" />
ReplaceEnumerationWithIterator
Since: PMD 3.4
Priority: Medium (3)
Consider replacing Enumeration usages with the newer java.util.Iterator
This rule is defined by the following XPath expression:
//ImplementsList/ClassOrInterfaceType[@Image='Enumeration']
Example(s):
public class Foo implements Enumeration {
private int x = 42;
public boolean hasMoreElements() {
return true;
}
public Object nextElement() {
return String.valueOf(i++);
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/ReplaceEnumerationWithIterator" />
ReplaceHashtableWithMap
Since: PMD 3.4
Priority: Medium (3)
Consider replacing Hashtable usage with the newer java.util.Map if thread safety is not required.
This rule is defined by the following XPath expression:
//Type/ReferenceType/ClassOrInterfaceType[@Image='Hashtable']
Example(s):
public class Foo {
void bar() {
Hashtable h = new Hashtable();
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/ReplaceHashtableWithMap" />
ReplaceVectorWithList
Since: PMD 3.4
Priority: Medium (3)
Consider replacing Vector usages with the newer java.util.ArrayList if expensive thread-safe operations are not required.
This rule is defined by the following XPath expression:
//Type/ReferenceType/ClassOrInterfaceType[@Image='Vector']
Example(s):
public class Foo {
void bar() {
Vector v = new Vector();
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/ReplaceVectorWithList" />
SimplifiableTestAssertion
Since: PMD 6.37.0
Priority: Medium (3)
Reports test assertions that may be simplified using a more specific assertion method. This enables better error messages, and makes the assertions more readable.
The rule only applies within test classes for the moment. It replaces
the deprecated rules UseAssertEqualsInsteadOfAssertTrue
,
UseAssertNullInsteadOfAssertTrue
, UseAssertSameInsteadOfAssertTrue
,
UseAssertTrueInsteadOfAssertEquals
, and SimplifyBooleanAssertion
.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.SimplifiableTestAssertionRule
Example(s):
import org.junit.Test;
import static org.junit.Assert.*;
class SomeTestClass {
Object a,b;
@Test
void testMethod() {
assertTrue(a.equals(b)); // could be assertEquals(a, b);
assertTrue(!a.equals(b)); // could be assertNotEquals(a, b);
assertTrue(!something); // could be assertFalse(something);
assertFalse(!something); // could be assertTrue(something);
assertTrue(a == b); // could be assertSame(a, b);
assertTrue(a != b); // could be assertNotSame(a, b);
assertTrue(a == null); // could be assertNull(a);
assertTrue(a != null); // could be assertNotNull(a);
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/SimplifiableTestAssertion" />
SwitchStmtsShouldHaveDefault
Since: PMD 1.0
Priority: Medium (3)
Switch statements should be exhaustive, to make their control flow
easier to follow. This can be achieved by adding a default
case, or,
if the switch is on an enum type, by ensuring there is one switch branch
for each enum constant.
This rule is defined by the following XPath expression:
//SwitchStatement[@DefaultCase = false() and @ExhaustiveEnumSwitch = false()]
Example(s):
class Foo {{
int x = 2;
switch (x) {
case 1: int j = 6;
case 2: int j = 8;
// missing default: here
}
}}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/SwitchStmtsShouldHaveDefault" />
SystemPrintln
Since: PMD 2.1
Priority: Medium High (2)
References to System.(out|err).print are usually intended for debugging purposes and can remain in the codebase even in production code. By using a logger one can enable/disable this behaviour at will (and by priority) and avoid clogging the Standard out log.
This rule is defined by the following XPath expression:
//Name[
starts-with(@Image, 'System.out.print')
or
starts-with(@Image, 'System.err.print')
]
Example(s):
class Foo{
Logger log = Logger.getLogger(Foo.class.getName());
public void testA () {
System.out.println("Entering test");
// Better use this
log.fine("Entering test");
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/SystemPrintln" />
UnusedAssignment
Since: PMD 6.26.0
Priority: Medium (3)
Reports assignments to variables that are never used before the variable is overwritten, or goes out of scope. Unused assignments are those for which
- The variable is never read after the assignment, or
- The assigned value is always overwritten by other assignments before the next read of the variable.
The rule doesn’t consider assignments to fields except for those of this
in a constructor,
or static fields of the current class in static initializers.
The rule may be suppressed with the standard @SuppressWarnings("unused")
tag.
The rule subsumes UnusedLocalVariable
, and UnusedFormalParameter
.
Those violations are filtered
out by default, in case you already have enabled those rules, but may be enabled with the property
reportUnusedVariables
. Variables whose name starts with ignored
or unused
are filtered out, as
is standard practice for exceptions.
Limitations:
- The rule currently cannot know which method calls throw exceptions, or which exceptions they throw.
In the body of a try block, every method or constructor call is assumed to throw. This may cause false-negatives.
The only other language construct that is assumed to throw is the
throw
statement, in particular, things likeassert
statements, or NullPointerExceptions on dereference are ignored. - The rule cannot resolve assignments across constructors, when they’re called with the special
this(...)
syntax. This may cause false-negatives.
Both of those limitations may be partly relaxed in PMD 7.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.UnusedAssignmentRule
Example(s):
class A {
// this field initializer is redundant,
// it is always overwritten in the constructor
int f = 1;
A(int f) {
this.f = f;
}
}
class B {
int method(int i, int j) {
// this initializer is redundant,
// it is overwritten in all branches of the `if`
int k = 0;
// Both the assignments to k are unused, because k is
// not read after the if/else
// This may hide a bug: the programmer probably wanted to return k
if (i < j)
k = i;
else
k = j;
return j;
}
}
class C {
int method() {
int i = 0;
checkSomething(++i);
checkSomething(++i);
checkSomething(++i);
checkSomething(++i);
// That last increment is not reported unless
// the property `checkUnusedPrefixIncrement` is
// set to `true`
// Technically it could be written (i+1), but it
// is not very important
}
}
class C {
// variables that are truly unused (at most assigned to, but never accessed)
// are only reported if property `reportUnusedVariables` is true
void method(int param) { } // for example this method parameter
// even then, you can suppress the violation with an annotation:
void method(@SuppressWarning("unused") int param) { } // no violation, even if `reportUnusedVariables` is true
// For catch parameters, or for resources which don't need to be used explicitly,
// you can give a name that starts with "ignored" to ignore such warnings
{
try (Something ignored = Something.create()) {
// even if ignored is unused, it won't be flagged
// its purpose might be to side-effect in the create/close routines
} catch (Exception e) { // this is unused and will cause a warning if `reportUnusedVariables` is true
// you should choose a name that starts with "ignored"
return;
}
}
}
This rule has the following properties:
Name | Default Value | Description | Multivalued |
---|---|---|---|
checkUnusedPrefixIncrement | false | Report expressions like ++i that may be replaced with (i + 1) | no |
reportUnusedVariables | false | Report variables that are only initialized, and never read at all. The rule UnusedVariable already cares for that, but you can enable it if needed | no |
Use this rule with the default properties by just referencing it:
<rule ref="category/java/bestpractices.xml/UnusedAssignment" />
Use this rule and customize it:
<rule ref="category/java/bestpractices.xml/UnusedAssignment">
<properties>
<property name="checkUnusedPrefixIncrement" value="false" />
<property name="reportUnusedVariables" value="false" />
</properties>
</rule>
UnusedFormalParameter
Since: PMD 0.8
Priority: Medium (3)
Reports parameters of methods and constructors that are not referenced them in the method body.
Parameters whose name starts with ignored
or unused
are filtered out.
Removing unused formal parameters from public methods could cause a ripple effect through the code base.
Hence, by default, this rule only considers private methods. To include non-private methods, set the
checkAll
property to true
.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.UnusedFormalParameterRule
Example(s):
public class Foo {
private void bar(String howdy) {
// howdy is not used
}
}
This rule has the following properties:
Name | Default Value | Description | Multivalued |
---|---|---|---|
checkAll | false | Check all methods, including non-private ones | no |
Use this rule with the default properties by just referencing it:
<rule ref="category/java/bestpractices.xml/UnusedFormalParameter" />
Use this rule and customize it:
<rule ref="category/java/bestpractices.xml/UnusedFormalParameter">
<properties>
<property name="checkAll" value="false" />
</properties>
</rule>
UnusedImports
Deprecated
Since: PMD 1.0
Priority: Medium Low (4)
Reports import statements that are not used within the file. This also reports duplicate imports, and imports from the same package. The simplest fix is just to delete those imports.
Note: This rule is deprecated since PMD 6.34.0 and will be removed with PMD 7.0.0.
Use the rule UnnecessaryImport
from category codestyle instead.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.UnusedImportsRule
Example(s):
import java.io.File; // not referenced or required
import java.util.*; // not referenced or required
public class Foo {}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/UnusedImports" />
UnusedLocalVariable
Since: PMD 0.1
Priority: Medium (3)
Detects when a local variable is declared and/or assigned, but not used.
Variables whose name starts with ignored
or unused
are filtered out.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.UnusedLocalVariableRule
Example(s):
public class Foo {
public void doSomething() {
int i = 5; // Unused
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/UnusedLocalVariable" />
UnusedPrivateField
Since: PMD 0.1
Priority: Medium (3)
Detects when a private field is declared and/or assigned a value, but not used.
Since PMD 6.50.0 private fields are ignored, if the fields are annotated with any annotation or the enclosing class has any annotation. Annotations often enable a framework (such as dependency injection, mocking or e.g. Lombok) which use the fields by reflection or other means. This usage can’t be detected by static code analysis. Previously these frameworks where explicitly allowed by listing their annotations in the property "ignoredAnnotations", but that turned out to be prone of false positive for any not explicitly considered framework.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.UnusedPrivateFieldRule
Example(s):
public class Something {
private static int FOO = 2; // Unused
private int i = 5; // Unused
private int j = 6;
public int addOne() {
return j++;
}
}
This rule has the following properties:
Name | Default Value | Description | Multivalued |
---|---|---|---|
ignoredAnnotations | Deprecated Fully qualified names of the annotation types that should be ignored by this rule. This property has been deprecated since PMD 6.50.0 and will be completely ignored. | yes. Delimiter is ‘|’. | |
ignoredFieldNames | serialVersionUID | serialPersistentFields | Field Names that are ignored from the unused check | yes. Delimiter is ‘|’. |
reportForAnnotations | Fully qualified names of the annotation types that should be reported anyway. If an unused field has any of these annotations, then it is reported. If it has any other annotation, then it is still considered to used and is not reported. | yes. Delimiter is ‘|’. |
Use this rule with the default properties by just referencing it:
<rule ref="category/java/bestpractices.xml/UnusedPrivateField" />
Use this rule and customize it:
<rule ref="category/java/bestpractices.xml/UnusedPrivateField">
<properties>
<property name="ignoredFieldNames" value="serialVersionUID|serialPersistentFields" />
<property name="reportForAnnotations" value="" />
</properties>
</rule>
UnusedPrivateMethod
Since: PMD 0.7
Priority: Medium (3)
Unused Private Method detects when a private method is declared but is unused.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.UnusedPrivateMethodRule
Example(s):
public class Something {
private void foo() {} // unused
}
This rule has the following properties:
Name | Default Value | Description | Multivalued |
---|---|---|---|
ignoredAnnotations | java.lang.Deprecated | Fully qualified names of the annotation types that should be ignored by this rule | yes. Delimiter is ‘|’. |
Use this rule with the default properties by just referencing it:
<rule ref="category/java/bestpractices.xml/UnusedPrivateMethod" />
Use this rule and customize it:
<rule ref="category/java/bestpractices.xml/UnusedPrivateMethod">
<properties>
<property name="ignoredAnnotations" value="java.lang.Deprecated" />
</properties>
</rule>
UseAssertEqualsInsteadOfAssertTrue
Deprecated
Since: PMD 3.1
Priority: Medium (3)
This rule detects JUnit assertions in object equality. These assertions should be made by more specific methods, like assertEquals.
Note: This rule is deprecated since PMD 6.37.0 and will be removed with PMD 7.0.0.
Use SimplifiableTestAssertion
instead.
This rule is defined by the following XPath expression:
//ClassOrInterfaceDeclaration[
pmd-java:typeIs('junit.framework.TestCase')
or .//MarkerAnnotation/Name[
pmd-java:typeIs('org.junit.Test')
or pmd-java:typeIs('org.junit.jupiter.api.Test')
or pmd-java:typeIs('org.junit.jupiter.api.RepeatedTest')
or pmd-java:typeIs('org.junit.jupiter.api.TestFactory')
or pmd-java:typeIs('org.junit.jupiter.api.TestTemplate')
or pmd-java:typeIs('org.junit.jupiter.params.ParameterizedTest')
]
]
//PrimaryExpression[
PrimaryPrefix/Name[@Image = 'assertTrue']
][
PrimarySuffix/Arguments/ArgumentList/Expression/PrimaryExpression/PrimaryPrefix/Name
[ends-with(@Image, '.equals')]
]
Example(s):
public class FooTest extends TestCase {
void testCode() {
Object a, b;
assertTrue(a.equals(b)); // bad usage
assertEquals("a should equals b", a, b); // good usage
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/UseAssertEqualsInsteadOfAssertTrue" />
UseAssertNullInsteadOfAssertTrue
Deprecated
Since: PMD 3.5
Priority: Medium (3)
This rule detects JUnit assertions in object references equality. These assertions should be made by more specific methods, like assertNull, assertNotNull.
Note: This rule is deprecated since PMD 6.37.0 and will be removed with PMD 7.0.0.
Use SimplifiableTestAssertion
instead.
This rule is defined by the following XPath expression:
//ClassOrInterfaceDeclaration[
pmd-java:typeIs('junit.framework.TestCase')
or .//MarkerAnnotation/Name[
pmd-java:typeIs('org.junit.Test')
or pmd-java:typeIs('org.junit.jupiter.api.Test')
or pmd-java:typeIs('org.junit.jupiter.api.RepeatedTest')
or pmd-java:typeIs('org.junit.jupiter.api.TestFactory')
or pmd-java:typeIs('org.junit.jupiter.api.TestTemplate')
or pmd-java:typeIs('org.junit.jupiter.params.ParameterizedTest')
]
]
//PrimaryExpression[
PrimaryPrefix/Name[@Image = 'assertTrue' or @Image = 'assertFalse']
][
PrimarySuffix/Arguments/ArgumentList[
Expression/EqualityExpression/PrimaryExpression/PrimaryPrefix/Literal/NullLiteral
]
]
Example(s):
public class FooTest extends TestCase {
void testCode() {
Object a = doSomething();
assertTrue(a==null); // bad usage
assertNull(a); // good usage
assertTrue(a != null); // bad usage
assertNotNull(a); // good usage
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/UseAssertNullInsteadOfAssertTrue" />
UseAssertSameInsteadOfAssertTrue
Deprecated
Since: PMD 3.1
Priority: Medium (3)
This rule detects JUnit assertions in object references equality. These assertions should be made by more specific methods, like assertSame, assertNotSame.
Note: This rule is deprecated since PMD 6.37.0 and will be removed with PMD 7.0.0.
Use SimplifiableTestAssertion
instead.
This rule is defined by the following XPath expression:
//ClassOrInterfaceDeclaration[
pmd-java:typeIs('junit.framework.TestCase')
or .//MarkerAnnotation/Name[
pmd-java:typeIs('org.junit.Test')
or pmd-java:typeIs('org.junit.jupiter.api.Test')
or pmd-java:typeIs('org.junit.jupiter.api.RepeatedTest')
or pmd-java:typeIs('org.junit.jupiter.api.TestFactory')
or pmd-java:typeIs('org.junit.jupiter.api.TestTemplate')
or pmd-java:typeIs('org.junit.jupiter.params.ParameterizedTest')
]
]
//PrimaryExpression[
PrimaryPrefix/Name[@Image = 'assertTrue' or @Image = 'assertFalse']
]
[
PrimarySuffix/Arguments/ArgumentList/Expression/EqualityExpression
[not(.//NullLiteral)]
]
Example(s):
public class FooTest extends TestCase {
void testCode() {
Object a, b;
assertTrue(a == b); // bad usage
assertSame(a, b); // good usage
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/UseAssertSameInsteadOfAssertTrue" />
UseAssertTrueInsteadOfAssertEquals
Deprecated
Since: PMD 5.0
Priority: Medium (3)
When asserting a value is the same as a literal or Boxed boolean, use assertTrue/assertFalse, instead of assertEquals.
Note: This rule is deprecated since PMD 6.37.0 and will be removed with PMD 7.0.0.
Use SimplifiableTestAssertion
instead.
This rule is defined by the following XPath expression:
//PrimaryExpression[PrimaryPrefix/Name[@Image = 'assertEquals']]
[
PrimarySuffix/Arguments/ArgumentList/Expression/PrimaryExpression/PrimaryPrefix/Literal/BooleanLiteral
or
PrimarySuffix/Arguments/ArgumentList/Expression/PrimaryExpression/PrimaryPrefix
/Name[(@Image = 'Boolean.TRUE' or @Image = 'Boolean.FALSE')]
]
Example(s):
public class MyTestCase extends TestCase {
public void testMyCase() {
boolean myVar = true;
// Ok
assertTrue("myVar is true", myVar);
// Bad
assertEquals("myVar is true", true, myVar);
// Bad
assertEquals("myVar is false", false, myVar);
// Bad
assertEquals("myVar is true", Boolean.TRUE, myVar);
// Bad
assertEquals("myVar is false", Boolean.FALSE, myVar);
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/UseAssertTrueInsteadOfAssertEquals" />
UseCollectionIsEmpty
Since: PMD 3.9
Priority: Medium (3)
The isEmpty() method on java.util.Collection is provided to determine if a collection has any elements. Comparing the value of size() to 0 does not convey intent as well as the isEmpty() method.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.UseCollectionIsEmptyRule
Example(s):
public class Foo {
void good() {
List foo = getList();
if (foo.isEmpty()) {
// blah
}
}
void bad() {
List foo = getList();
if (foo.size() == 0) {
// blah
}
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/UseCollectionIsEmpty" />
UseStandardCharsets
Since: PMD 6.34.0
Priority: Medium (3)
Minimum Language Version: Java 1.7
Starting with Java 7, StandardCharsets provides constants for common Charset objects, such as UTF-8.
Using the constants is less error prone, and can provide a small performance advantage compared to Charset.forName(...)
since no scan across the internal Charset
caches is needed.
This rule is defined by the following XPath expression:
//PrimaryExpression[PrimaryPrefix/Name/@Image = 'Charset.forName']
/PrimarySuffix/Arguments/ArgumentList/Expression/PrimaryExpression/PrimaryPrefix
/Literal[@Image = ('"US-ASCII"', '"ISO-8859-1"', '"UTF-8"', '"UTF-16BE"', '"UTF-16LE"', '"UTF-16"')]
Example(s):
public class UseStandardCharsets {
public void run() {
// looking up the charset dynamically
try (OutputStreamWriter osw = new OutputStreamWriter(out, Charset.forName("UTF-8"))) {
osw.write("test");
}
// best to use StandardCharsets
try (OutputStreamWriter osw = new OutputStreamWriter(out, StandardCharsets.UTF_8)) {
osw.write("test");
}
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/UseStandardCharsets" />
UseTryWithResources
Since: PMD 6.12.0
Priority: Medium (3)
Minimum Language Version: Java 1.7
Java 7 introduced the try-with-resources statement. This statement ensures that each resource is closed at the end
of the statement. It avoids the need of explicitly closing the resources in a finally block. Additionally exceptions
are better handled: If an exception occurred both in the try
block and finally
block, then the exception from
the try block was suppressed. With the try
-with-resources statement, the exception thrown from the try-block is
preserved.
This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.bestpractices.UseTryWithResourcesRule
Example(s):
public class TryWithResources {
public void run() {
InputStream in = null;
try {
in = openInputStream();
int i = in.read();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (in != null) in.close();
} catch (IOException ignored) {
// ignored
}
}
// better use try-with-resources
try (InputStream in2 = openInputStream()) {
int i = in2.read();
}
}
}
This rule has the following properties:
Name | Default Value | Description | Multivalued |
---|---|---|---|
closeMethods | close , closeQuietly | Method names in finally block, which trigger this rule | yes. Delimiter is ‘,’. |
Use this rule with the default properties by just referencing it:
<rule ref="category/java/bestpractices.xml/UseTryWithResources" />
Use this rule and customize it:
<rule ref="category/java/bestpractices.xml/UseTryWithResources">
<properties>
<property name="closeMethods" value="close,closeQuietly" />
</properties>
</rule>
UseVarargs
Since: PMD 5.0
Priority: Medium Low (4)
Minimum Language Version: Java 1.5
Java 5 introduced the varargs parameter declaration for methods and constructors. This syntactic sugar provides flexibility for users of these methods and constructors, allowing them to avoid having to deal with the creation of an array.
Byte arrays in any method and String arrays in public static void main(String[])
methods are ignored.
This rule is defined by the following XPath expression:
//FormalParameters/FormalParameter
[position()=last()]
[VariableDeclaratorId/@ArrayType=true()]
[@Varargs=false()]
[not (./Type[@ArrayType=true()]/ReferenceType[PrimitiveType[@Image='byte']])]
[not (./Type/ReferenceType[ClassOrInterfaceType[@Image='Byte']])]
[not (./Type/PrimitiveType[@Image='byte'])]
[not (ancestor::MethodDeclaration/preceding-sibling::Annotation/*/Name[@Image='Override'])]
[not(
ancestor::MethodDeclaration
[ @Public=true()
and @Static=true()
and child::ResultType[@Void=true()]
and @Name = 'main'
and @Arity = 1
]
(: Type of the formal parameter here. :)
and pmd-java:typeIs('java.lang.String[]')
)]
Example(s):
public class Foo {
public void foo(String s, Object[] args) {
// Do something here...
}
public void bar(String s, Object... args) {
// Ahh, varargs tastes much better...
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/UseVarargs" />
WhileLoopWithLiteralBoolean
Since: PMD 6.13.0
Priority: Medium (3)
do {} while (true);
requires reading the end of the statement before it is
apparent that it loops forever, whereas while (true) {}
is easier to understand.
do {} while (false);
is redundant, and if an inner variable scope is required,
a block {}
is sufficient.
while (false) {}
will never execute the block and can be removed in its entirety.
This rule is defined by the following XPath expression:
(: while loops with single boolean literal 'false', maybe parenthesized :)
//WhileStatement[Expression/(.|(PrimaryExpression/PrimaryPrefix/Expression))/PrimaryExpression/PrimaryPrefix/Literal/BooleanLiteral[@True = false()]]
|
(: do-while loops with single boolean literal ('false' or 'true'), maybe parenthesized :)
//DoStatement[Expression/(.|(PrimaryExpression/PrimaryPrefix/Expression))/PrimaryExpression/PrimaryPrefix/Literal/BooleanLiteral]
|
(: while loops with conditional or'ed boolean literals, maybe parenthesized :)
//WhileStatement[Expression/(InclusiveOrExpression|ConditionalOrExpression|(PrimaryExpression/PrimaryPrefix/Expression/(InclusiveOrExpression|ConditionalOrExpression)))
(: no var access :)
[count(PrimaryExpression/PrimaryPrefix/Name) = 0]
(: at least one false literal :)
[count(PrimaryExpression/PrimaryPrefix/Literal/BooleanLiteral[@True = false()]) >= 1]]
|
(: while loops with conditional and'ed boolean literals, maybe parenthesized :)
//WhileStatement[Expression/(AndExpression|ConditionalAndExpression|(PrimaryExpression/PrimaryPrefix/Expression/(AndExpression|ConditionalAndExpression)))
(: at least one false literal :)
[count(PrimaryExpression/PrimaryPrefix/Literal/BooleanLiteral[@True = false()]) >= 1]]
|
(: do-while loops with conditional or'ed boolean literals, maybe parenthesized :)
//DoStatement[Expression/(InclusiveOrExpression|ConditionalOrExpression|(PrimaryExpression/PrimaryPrefix/Expression/(InclusiveOrExpression|ConditionalOrExpression)))
(: at least one true literal :)
[count(PrimaryExpression/PrimaryPrefix/Literal/BooleanLiteral[@True = true()]) >= 1
(: or only boolean literal and no no var access :)
or count(PrimaryExpression/PrimaryPrefix/Literal/BooleanLiteral) >= 1
and count(PrimaryExpression/PrimaryPrefix/Name) = 0
]]
|
(: do-while loops with conditional and'ed boolean literals, maybe parenthesized :)
//DoStatement[Expression/(AndExpression|ConditionalAndExpression|(PrimaryExpression/PrimaryPrefix/Expression/(AndExpression|ConditionalAndExpression)))
(: at least one false literal :)
[count(PrimaryExpression/PrimaryPrefix/Literal/BooleanLiteral[@True = false()]) >= 1
(: or only boolean literal and no no var access :)
or count(PrimaryExpression/PrimaryPrefix/Literal/BooleanLiteral) >= 1
and count(PrimaryExpression/PrimaryPrefix/Name) = 0
]]
Example(s):
public class Example {
{
while (true) { } // allowed
while (false) { } // disallowed
do { } while (true); // disallowed
do { } while (false); // disallowed
do { } while (false | false); // disallowed
do { } while (false || false); // disallowed
}
}
Use this rule by referencing it:
<rule ref="category/java/bestpractices.xml/WhileLoopWithLiteralBoolean" />