Module java.base
Package java.lang.constant

Interface ClassDesc

All Superinterfaces:
ConstantDesc, TypeDescriptor, TypeDescriptor.OfField<ClassDesc>
public interface ClassDesc
extends ConstantDesc, TypeDescriptor.OfField<ClassDesc>
A nominal descriptor for a Class constant.

For common system types, including all the primitive types, there are predefined ClassDesc constants in ConstantDescs. (The java.lang.constant APIs consider void to be a primitive type.) To create a ClassDesc for a class or interface type, use of(java.lang.String) or ofDescriptor(String); to create a ClassDesc for an array type, use ofDescriptor(String), or first obtain a ClassDesc for the component type and then call the arrayType() or arrayType(int) methods.

API Note:
In the future, if the Java language permits, ClassDesc may become a sealed interface, which would prohibit subclassing except by explicitly permitted types. Non-platform classes should not implement ClassDesc directly.
Since:
12
See Also:
ConstantDescs

  • Method Details

    • of

      static ClassDesc of​(String name)
      Returns a ClassDesc for a class or interface type, given the name of the class or interface, such as "java.lang.String". (To create a descriptor for an array type, either use ofDescriptor(String) or arrayType(); to create a descriptor for a primitive type, use ofDescriptor(String) or use the predefined constants in ConstantDescs).
      Parameters:
      name - the fully qualified (dot-separated) binary class name
      Returns:
      a ClassDesc describing the desired class
      Throws:
      NullPointerException - if the argument is null
      IllegalArgumentException - if the name string is not in the correct format

    • of

      static ClassDesc of​(String packageName, String className)
      Returns a ClassDesc for a class or interface type, given a package name and the unqualified (simple) name for the class or interface.
      Parameters:
      packageName - the package name (dot-separated); if the package name is the empty string, the class is considered to be in the unnamed package
      className - the unqualified (simple) class name
      Returns:
      a ClassDesc describing the desired class
      Throws:
      NullPointerException - if any argument is null
      IllegalArgumentException - if the package name or class name are not in the correct format

    • ofDescriptor

      static ClassDesc ofDescriptor​(String descriptor)
      Returns a ClassDesc given a descriptor string for a class, interface, array, or primitive type.
      API Note:
      A field type descriptor string for a non-array type is either a one-letter code corresponding to a primitive type ("J", "I", "C", "S", "B", "D", "F", "Z", "V"), or the letter "L", followed by the fully qualified binary name of a class, followed by ";". A field type descriptor for an array type is the character "[" followed by the field descriptor for the component type. Examples of valid type descriptor strings include "Ljava/lang/String;", "I", "[I", "V", "[Ljava/lang/String;", etc. See JVMS 4.3.2 ("Field Descriptors") for more detail.
      Parameters:
      descriptor - a field descriptor string
      Returns:
      a ClassDesc describing the desired class
      Throws:
      NullPointerException - if the argument is null
      IllegalArgumentException - if the name string is not in the correct format
      See Java Virtual Machine Specification:
      4.3.2 Field Descriptors
      4.4.1 The CONSTANT_Class_info Structure

    • arrayType

      default ClassDesc arrayType()
      Returns a ClassDesc for an array type whose component type is described by this ClassDesc.
      Specified by:
      arrayType in interface TypeDescriptor.OfField<ClassDesc>
      Returns:
      a ClassDesc describing the array type
      Throws:
      IllegalStateException - if the resulting ClassDesc would have an array rank of greater than 255
      See Java Virtual Machine Specification:
      4.4.1 The CONSTANT_Class_info Structure

    • arrayType

      default ClassDesc arrayType​(int rank)
      Returns a ClassDesc for an array type of the specified rank, whose component type is described by this ClassDesc.
      Parameters:
      rank - the rank of the array
      Returns:
      a ClassDesc describing the array type
      Throws:
      IllegalArgumentException - if the rank is less than or equal to zero or if the rank of the resulting array type is greater than 255
      See Java Virtual Machine Specification:
      4.4.1 The CONSTANT_Class_info Structure

    • nested

      default ClassDesc nested​(String nestedName)
      Returns a ClassDesc for a nested class of the class or interface type described by this ClassDesc.
      API Note:
      Example: If descriptor d describes the class java.util.Map, a descriptor for the class java.util.Map.Entry could be obtained by d.nested("Entry").
      Parameters:
      nestedName - the unqualified name of the nested class
      Returns:
      a ClassDesc describing the nested class
      Throws:
      NullPointerException - if the argument is null
      IllegalStateException - if this ClassDesc does not describe a class or interface type
      IllegalArgumentException - if the nested class name is invalid

    • nested

      default ClassDesc nested​(String firstNestedName, String... moreNestedNames)
      Returns a ClassDesc for a nested class of the class or interface type described by this ClassDesc.
      Parameters:
      firstNestedName - the unqualified name of the first level of nested class
      moreNestedNames - the unqualified name(s) of the remaining levels of nested class
      Returns:
      a ClassDesc describing the nested class
      Throws:
      NullPointerException - if any argument or its contents is null
      IllegalStateException - if this ClassDesc does not describe a class or interface type
      IllegalArgumentException - if the nested class name is invalid

    • isArray

      default boolean isArray()
      Returns whether this ClassDesc describes an array type.
      Specified by:
      isArray in interface TypeDescriptor.OfField<ClassDesc>
      Returns:
      whether this ClassDesc describes an array type

    • isPrimitive

      default boolean isPrimitive()
      Returns whether this ClassDesc describes a primitive type.
      Specified by:
      isPrimitive in interface TypeDescriptor.OfField<ClassDesc>
      Returns:
      whether this ClassDesc describes a primitive type

    • isClassOrInterface

      default boolean isClassOrInterface()
      Returns whether this ClassDesc describes a class or interface type.
      Returns:
      whether this ClassDesc describes a class or interface type

    • componentType

      default ClassDesc componentType()
      Returns the component type of this ClassDesc, if it describes an array type, or null otherwise.
      Specified by:
      componentType in interface TypeDescriptor.OfField<ClassDesc>
      Returns:
      a ClassDesc describing the component type, or null if this descriptor does not describe an array type

    • packageName

      default String packageName()
      Returns the package name of this ClassDesc, if it describes a class or interface type.
      Returns:
      the package name, or the empty string if the class is in the default package, or this ClassDesc does not describe a class or interface type

    • displayName

      default String displayName()
      Returns a human-readable name for the type described by this descriptor.
      Implementation Requirements:

      The default implementation returns the simple name (e.g., int) for primitive types, the unqualified class name for class or interface types, or the display name of the component type suffixed with the appropriate number of [] pairs for array types.

      Returns:
      the human-readable name

    • descriptorString

      String descriptorString()
      Returns a field type descriptor string for this type
      Specified by:
      descriptorString in interface TypeDescriptor
      Returns:
      the descriptor string
      See Java Virtual Machine Specification:
      4.3.2 Field Descriptors

    • equals

      boolean equals​(Object o)
      Compare the specified object with this descriptor for equality. Returns true if and only if the specified object is also a ClassDesc and both describe the same type.
      Overrides:
      equals in class Object
      Parameters:
      o - the other object
      Returns:
      whether this descriptor is equal to the other object
      See Also:
      Object.hashCode(), HashMap