Constable interface in Java

java.lang.constant.Constable

Represents a type that is constable. A constable type is one whose values are constants that can be represented in the constant pool of a Java class file.

Some constable types have a native representation in the constant pool:

String, Integer, Long, Float, Double, Class, MethodType, and MethodHandle.The types String, Integer, Long, Float, and Double serve as their own nominal descriptors; Class, MethodType, and MethodHandle have the corresponding nominal descriptors ClassDesc, MethodTypeDesc, and MethodHandleDesc.

Declaration

public interface Constable {

    Optional<? extends ConstantDesc> describeConstable();
}

Methods

1. describeConstable()

Optional<? extends ConstantDesc> java.lang.constant.Constable.describeConstable()

This method returns an Optional containing the nominal descriptor for this instance, if one can be constructed, or an empty Optional if one cannot be constructed.

Parameters: NA

Returns: An Optional containing the resulting nominal descriptor, or an empty Optional if one cannot be constructed.

Exceptions: NA

Some other classes/interfaces of java.lang.constant

MethodTypeDesc: A nominal descriptor for a MethodType constant.

MethodHandleDesc: A nominal descriptor for a MethodHandle constant.

DynamicConstantDesc: A nominal descriptor for a dynamic constant.

DynamicCallSiteDesc: A nominal descriptor for an invoke dynamic call site.

DirectMethodHandleDesc: A nominal descriptor for a direct MethodHandle. A DirectMethodHandleDesc corresponds to a Constant_MethodHandle_info entry in the constant pool of a class file.

ConstantDescs: Predefined values of nominal descriptors for common constants, including descriptors for primitive class types and other common platform types, and descriptors for method handles for standard bootstrap methods.

ConstantDesc: A nominal descriptor for a loadable constant value. Such a descriptor can be resolved via ConstantDesc.resolveConstantDesc(MethodHandles.Lookup) to yield the constant value itself.

Constable: Represents a type that is constable. A constable type is one whose values are constants that can be represented in the constant pool of a Java class file.

ClassDesc: A nominal descriptor for a Class constant.