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Enum Class TypeKind

java.lang.Object

java.lang.Enum<TypeKind>

java.lang.classfile.TypeKind

All Implemented Interfaces:: Serializable, Comparable<TypeKind>, Constable

public enum TypeKind extends Enum<TypeKind>

Describes the data types Java Virtual Machine operates on. This omits


returnAddress

(JVMS 2.3.3) and includes void (JVMS 4.3.3), which appears as a method return type.

The returnAddress type is only used by discontinued jump subroutine and return from subroutine instructions. Jump subroutine instructions push returnAddress to the operand stack; astore instructions store returnAddress from the operand stack to local variables; return from subroutine instructions load returnAddress from local variables.

Computational Type

In the class file format, local variables (JVMS 2.6.1), and the operand stack (JVMS 2.6.2) of the Java Virtual Machine, boolean, byte, char, short types do not exist and are represented by the int computational type. int, float, reference, returnAddress, long, and doule are the computational types of the Java Virtual Machine.

See Java Virtual Machine Specification:: 2.2 Data Types
2.11.1 Types and the Java Virtual Machine
Since:: 24

Nested Class Summary

Nested classes/interfaces declared in class Enum

Enum.EnumDesc<E>

Enum Constant Summary

Enum Constant	Description
`BOOLEAN`	The primitive type `boolean`.
`BYTE`	The primitive type `byte`.
`CHAR`	The primitive type `char`.
`DOUBLE`	The primitive type `double`.
`FLOAT`	The primitive type `float`.
`INT`	The primitive type `int`.
`LONG`	The primitive type `long`.
`REFERENCE`	A reference type.
`SHORT`	The primitive type `short`.
`VOID`	The `void` type, for absence of a value.

Method Summary

Modifier and Type	Method	Description
`TypeKind`	`asLoadable()`	Returns the computational type for this type, or `void` for `void`.
`static TypeKind`	`from(TypeDescriptor.OfField<?> descriptor)`	Returns the type associated with the specified field descriptor.
`static TypeKind`	`fromDescriptor(CharSequence s)`	Returns the type associated with the specified field descriptor.
`static TypeKind`	`fromNewarrayCode(int newarrayCode)`	Returns the component type described by the array code used as an operand to `newarray`.
`int`	`newarrayCode()`	Returns the code used by the `newarray` instruction to create an array of this component type, or `-1` if this type is not supported by `newarray`.
`int`	`slotSize()`	Returns the number of local variable index or operand stack depth consumed by this type.
`ClassDesc`	`upperBound()`	Returns the most specific upper bound field descriptor that can store any value of this type.
`static TypeKind`	`valueOf(String name)`	Returns the enum constant of this class with the specified name.
`static TypeKind[]`	`values()`	Returns an array containing the constants of this enum class, in the order they are declared.

Methods declared in class Enum

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

Methods declared in class Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Details

BOOLEAN

public static final TypeKind BOOLEAN

The primitive type boolean. Its computational type is int. 0 represents false, and 1 represents true. It is zero-extended to an int when loaded onto the operand stack and narrowed by taking the bitwise AND with 1 when stored.

See Java Virtual Machine Specification:: 2.3.4 The boolean Type

BYTE

public static final TypeKind BYTE

The primitive type byte. Its computational type is int. It is sign-extended to an int when loaded onto the operand stack and truncated when stored.

CHAR

public static final TypeKind CHAR

The primitive type char. Its computational type is int. It is zero-extended to an int when loaded onto the operand stack and truncated when stored.

SHORT

public static final TypeKind SHORT

The primitive type short. Its computational type is int. It is sign-extended to an int when loaded onto the operand stack and truncated when stored.

INT

public static final TypeKind INT

The primitive type int.

LONG

public static final TypeKind LONG

The primitive type long. It is of category 2.

FLOAT

public static final TypeKind FLOAT

The primitive type float. All NaN values of float may or may not be collapsed into a single "canonical" NaN value in loading and storing.

DOUBLE

public static final TypeKind DOUBLE

The primitive type double. It is of category 2. All NaN values of double may or may not be collapsed into a single "canonical" NaN value in loading and storing.

REFERENCE

public static final TypeKind REFERENCE

A reference type.

See Java Virtual Machine Specification:: 2.4 Reference Types and Values

VOID

public static final TypeKind VOID

The void type, for absence of a value. While this is not a data type, this can be a method return type indicating no change in operand stack depth.

See Java Virtual Machine Specification:: 4.3.3 Method Descriptors

Method Details

values

public static TypeKind[] values()

Returns an array containing the constants of this enum class, in the order they are declared.

Returns:: an array containing the constants of this enum class, in the order they are declared

valueOf

public static TypeKind valueOf(String name)

Returns the enum constant of this class with the specified name. The string must match exactly an identifier used to declare an enum constant in this class. (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 class has no constant with the specified name; NullPointerException - if the argument is null

upperBound

public ClassDesc upperBound()

Returns the most specific upper bound field descriptor that can store any value of this type. This is the primitive class descriptor for primitive types and void and Object descriptor for reference.

Returns:: the most specific upper bound field descriptor that can store any value of this type

newarrayCode

public int newarrayCode()

Returns the code used by the newarray instruction to create an array of this component type, or -1 if this type is not supported by newarray.

Returns:

the code used by the newarray instruction to create an array of this component type, or -1 if this type is not supported by newarray

See Java Virtual Machine Specification:

6.5.newarray newarray

See Also:

slotSize

public int slotSize()

Returns the number of local variable index or operand stack depth consumed by this type. This is also the category of this type for instructions operating on the operand stack without regard to type (JVMS 2.11.1), such as pop versus pop2.

Returns:: the number of local variable index or operand stack depth consumed by this type
See Java Virtual Machine Specification:: 2.6.1 Local Variables
2.6.2 Operand Stacks

asLoadable

public TypeKind asLoadable()

Returns the computational type for this type, or void for void.

Returns:

the computational type for this type, or void for void

See Also:

fromNewarrayCode

public static TypeKind fromNewarrayCode(int newarrayCode)

Returns the component type described by the array code used as an operand to newarray.

Parameters:

newarrayCode - the operand of the newarray instruction

Returns:

the component type described by the array code used as an operand to newarray

Throws:

IllegalArgumentException - if the code is invalid

See Java Virtual Machine Specification:

6.5.newarray newarray

See Also:

fromDescriptor

public static TypeKind fromDescriptor(CharSequence s)

Returns the type associated with the specified field descriptor.

Parameters:: s - the field descriptor
Returns:: the type associated with the specified field descriptor
Throws:: IllegalArgumentException - only if the descriptor is not valid

from

public static TypeKind from(TypeDescriptor.OfField<?> descriptor)

Returns the type associated with the specified field descriptor.

Parameters:: descriptor - the field descriptor
Returns:: the type associated with the specified field descriptor

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https://docs.oracle.com/en/java/javase/25/docs/api/java.base/java/lang/classfile/TypeKind.html