Module java.base

Class DynamicConstantDesc<T>

java.lang.Object
java.lang.constant.DynamicConstantDesc<T>
Type Parameters:
T - the type of the dynamic constant
All Implemented Interfaces:
ConstantDesc
Direct Known Subclasses:
Enum.EnumDesc, VarHandle.VarHandleDesc

public abstract class DynamicConstantDesc<T> extends Object implements ConstantDesc
A nominal descriptor for a dynamic constant (one described in the constant pool with Constant_Dynamic_info.)

Concrete subtypes of DynamicConstantDesc should be immutable and their behavior should not rely on object identity.

Since:
12
  • Constructor Details

    • DynamicConstantDesc

      protected DynamicConstantDesc(DirectMethodHandleDesc bootstrapMethod, String constantName, ClassDesc constantType, ConstantDesc... bootstrapArgs)
      Creates a nominal descriptor for a dynamic constant.
      Parameters:
      bootstrapMethod - a DirectMethodHandleDesc describing the bootstrap method for the constant
      constantName - The unqualified name that would appear in the NameAndType operand of the LDC for this constant
      constantType - a ClassDesc describing the type that would appear in the NameAndType operand of the LDC for this constant
      bootstrapArgs - ConstantDescs describing the static arguments to the bootstrap, that would appear in the BootstrapMethods attribute
      Throws:
      NullPointerException - if any argument is null
      IllegalArgumentException - if the name has the incorrect format
      See Java Virtual Machine Specification:
      4.2.2 Unqualified Names
  • Method Details

    • ofCanonical

      public static <T> ConstantDesc ofCanonical(DirectMethodHandleDesc bootstrapMethod, String constantName, ClassDesc constantType, ConstantDesc[] bootstrapArgs)
      Returns a nominal descriptor for a dynamic constant, transforming it into a more specific type if the constant bootstrap is a well-known one and a more specific nominal descriptor type (e.g., ClassDesc) is available.

      Classes whose Constable.describeConstable() method produce a DynamicConstantDesc with a well-known bootstrap including Class (for instances describing primitive types), Enum, and VarHandle.

      Bytecode-reading APIs that process the constant pool and wish to expose entries as ConstantDesc to their callers should generally use this method in preference to ofNamed(DirectMethodHandleDesc, String, ClassDesc, ConstantDesc...) because this may result in a more specific type that can be provided to callers.

      Type Parameters:
      T - the type of the dynamic constant
      Parameters:
      bootstrapMethod - a DirectMethodHandleDesc describing the bootstrap method for the constant
      constantName - The unqualified name that would appear in the NameAndType operand of the LDC for this constant
      constantType - a ClassDesc describing the type that would appear in the NameAndType operand of the LDC for this constant
      bootstrapArgs - ConstantDescs describing the static arguments to the bootstrap, that would appear in the BootstrapMethods attribute
      Returns:
      the nominal descriptor
      Throws:
      NullPointerException - if any argument is null
      IllegalArgumentException - if the name has the incorrect format
      See Java Virtual Machine Specification:
      4.2.2 Unqualified Names
    • ofNamed

      public static <T> DynamicConstantDesc<T> ofNamed(DirectMethodHandleDesc bootstrapMethod, String constantName, ClassDesc constantType, ConstantDesc... bootstrapArgs)
      Returns a nominal descriptor for a dynamic constant.
      Type Parameters:
      T - the type of the dynamic constant
      Parameters:
      bootstrapMethod - a DirectMethodHandleDesc describing the bootstrap method for the constant
      constantName - The unqualified name that would appear in the NameAndType operand of the LDC for this constant
      constantType - a ClassDesc describing the type that would appear in the NameAndType operand of the LDC for this constant
      bootstrapArgs - ConstantDescs describing the static arguments to the bootstrap, that would appear in the BootstrapMethods attribute
      Returns:
      the nominal descriptor
      Throws:
      NullPointerException - if any argument is null
      IllegalArgumentException - if the name has the incorrect format
      See Java Virtual Machine Specification:
      4.2.2 Unqualified Names
    • of

      public static <T> DynamicConstantDesc<T> of(DirectMethodHandleDesc bootstrapMethod, ConstantDesc... bootstrapArgs)
      Returns a nominal descriptor for a dynamic constant whose name parameter is ConstantDescs.DEFAULT_NAME, and whose type parameter is always the same as the bootstrap method return type.
      Type Parameters:
      T - the type of the dynamic constant
      Parameters:
      bootstrapMethod - a DirectMethodHandleDesc describing the bootstrap method for the constant
      bootstrapArgs - ConstantDescs describing the static arguments to the bootstrap, that would appear in the BootstrapMethods attribute
      Returns:
      the nominal descriptor
      Throws:
      NullPointerException - if any argument is null
      See Java Virtual Machine Specification:
      4.2.2 Unqualified Names
    • of

      public static <T> DynamicConstantDesc<T> of(DirectMethodHandleDesc bootstrapMethod)
      Returns a nominal descriptor for a dynamic constant whose bootstrap has no static arguments, whose name parameter is ConstantDescs.DEFAULT_NAME, and whose type parameter is always the same as the bootstrap method return type.
      Type Parameters:
      T - the type of the dynamic constant
      Parameters:
      bootstrapMethod - a DirectMethodHandleDesc describing the bootstrap method for the constant
      Returns:
      the nominal descriptor
      Throws:
      NullPointerException - if any argument is null
    • constantName

      public String constantName()
      Returns the name that would appear in the NameAndType operand of the LDC for this constant.
      Returns:
      the constant name
    • constantType

      public ClassDesc constantType()
      Returns a ClassDesc describing the type that would appear in the NameAndType operand of the LDC for this constant.
      Returns:
      the constant type
    • bootstrapMethod

      public DirectMethodHandleDesc bootstrapMethod()
      Returns a MethodHandleDesc describing the bootstrap method for this constant.
      Returns:
      the bootstrap method
    • bootstrapArgs

      public ConstantDesc[] bootstrapArgs()
      Returns the bootstrap arguments for this constant.
      Returns:
      the bootstrap arguments
    • bootstrapArgsList

      public List<ConstantDesc> bootstrapArgsList()
      Returns the bootstrap arguments for this constant as an immutable List.
      Returns:
      a List of the bootstrap arguments
    • resolveConstantDesc

      public T resolveConstantDesc(MethodHandles.Lookup lookup) throws ReflectiveOperationException
      Description copied from interface: ConstantDesc
      Resolves this descriptor reflectively, emulating the resolution behavior of JVMS 5.4.3 and the access control behavior of JVMS 5.4.4. The resolution and access control context is provided by the MethodHandles.Lookup parameter. No caching of the resulting value is performed.
      Specified by:
      resolveConstantDesc in interface ConstantDesc
      Parameters:
      lookup - The MethodHandles.Lookup to provide name resolution and access control context
      Returns:
      the resolved constant value
      Throws:
      ReflectiveOperationException - if a class, method, or field could not be reflectively resolved in the course of resolution
    • equals

      public final boolean equals(Object o)
      Compares the specified object with this descriptor for equality. Returns true if and only if the specified object is also a DynamicConstantDesc, and both descriptors have equal bootstrap methods, bootstrap argument lists, constant name, and constant type.
      Overrides:
      equals in class Object
      Parameters:
      o - the DynamicConstantDesc to compare to this DynamicConstantDesc
      Returns:
      true if the specified DynamicConstantDesc is equal to this DynamicConstantDesc.
      See Also:
      Object.hashCode(), HashMap
    • hashCode

      public final int hashCode()
      Description copied from class: Object
      Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by HashMap.

      The general contract of hashCode is:

      • Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
      • If two objects are equal according to the equals method, then calling the hashCode method on each of the two objects must produce the same integer result.
      • It is not required that if two objects are unequal according to the equals method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.
      Overrides:
      hashCode in class Object
      Returns:
      a hash code value for this object.
      See Also:
      Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)
    • toString

      public String toString()
      Returns a compact textual description of this constant description, including the bootstrap method, the constant name and type, and the static bootstrap arguments.
      Overrides:
      toString in class Object
      Returns:
      A compact textual description of this call site descriptor