Package net.sourceforge.pmd.lang.java.types

Enum TypeOps.Convertibility

java.lang.Object

java.lang.Enum<TypeOps.Convertibility>

net.sourceforge.pmd.lang.java.types.TypeOps.Convertibility

All Implemented Interfaces:

Serializable, Comparable<TypeOps.Convertibility>

Enclosing class:

TypeOps

public static enum TypeOps.Convertibility
extends Enum<TypeOps.Convertibility>

A result for a convertibility check. This is a tiny generalization of a subtyping check.

Primitive types are implicitly convertible to each other by widening primitive conversion. For reference types, subtyping implies convertibility (the conversion is technically called "widening reference conversion"). You can check those cases using: t.isConvertibleTo(s).bySubtyping()

Unchecked conversion may go backwards from subtyping. For example, List<String> is a subtype of the raw type List, and as such is convertible to it by reference widening. But List may be "coerced" to List<String> with an unchecked warning: t.isConvertibleTo(s).withUncheckedWarning()

If the parameterized type only has wildcard type arguments, then the conversion produces no warning. t.isConvertibleTo(s) == UNCHECKED_NO_WARNING

Two types may be unconvertible: t.isConvertibleTo(s).never()

the negation of which being t.isConvertibleTo(s).somehow()

Note that this does not check for boxing or unboxing conversions, nor for narrowing conversions, which may happen through casts.

Enum Constant Summary

Enum Constants

Enum Constant	Description
NEVER	T is never implicitly convertible to S.
SUBTYPING	T is a subtype of S (T <: S).
UNCHECKED_NO_WARNING	T <: |S| and T </: S, but S is parameterized with only unbounded wildcards.
UNCHECKED_WARNING	T is not a subtype of S, but every time T is used in a context where an S is expected, unchecked conversion converts the T to an S with a mandated warning.

Method Summary

Modifier and Type	Method	Description
boolean	bySubtyping()	True if this is SUBTYPING.
boolean	never()	Returns true if this is NEVER.
boolean	somehow()	Returns true if this is anything but NEVER.
static TypeOps.Convertibility	valueOf(String name)	Returns the enum constant of this type with the specified name.
static TypeOps.Convertibility[]	values()	Returns an array containing the constants of this enum type, in the order they are declared.
boolean	withUncheckedWarning()	True if this is UNCHECKED_WARNING.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

NEVER

public static final TypeOps.Convertibility NEVER

T is never implicitly convertible to S.

UNCHECKED_WARNING

public static final TypeOps.Convertibility UNCHECKED_WARNING

T is not a subtype of S, but every time T is used in a context where an S is expected, unchecked conversion converts the T to an S with a mandated warning. For example the raw type Class is convertible to Class<String> with an unchecked warning.

UNCHECKED_NO_WARNING

public static final TypeOps.Convertibility UNCHECKED_NO_WARNING

T <: |S| and T </: S, but S is parameterized with only unbounded wildcards. This is a special case of unchecked conversion that produces no warning. We keep it distinct from subtyping to help some algorithms that require subtyping to be a partial order.

For example, List<String> is a subtype of the raw Collection, not a subtype of Collection<?>, but it is still convertible without warning.

SUBTYPING

public static final TypeOps.Convertibility SUBTYPING

T is a subtype of S (T <: S). In particular, any type is a subtype of itself (T <: T).

For example, int can be widened to long, so we consider int <: long.

Method Detail

values

public static TypeOps.Convertibility[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (TypeOps.Convertibility c : TypeOps.Convertibility.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static TypeOps.Convertibility valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

NullPointerException - if the argument is null

never

public boolean never()

Returns true if this is NEVER.

somehow

public boolean somehow()

Returns true if this is anything but NEVER.

bySubtyping

public boolean bySubtyping()

True if this is SUBTYPING.

withUncheckedWarning

public boolean withUncheckedWarning()

True if this is UNCHECKED_WARNING.