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Interface PoolEntry

public sealed interface PoolEntry permits AnnotationConstantValueEntry, DynamicConstantPoolEntry, LoadableConstantEntry, MemberRefEntry, ModuleEntry, NameAndTypeEntry, PackageEntry

Models an entry in the constant pool of a class file. Entries are read from class files, and can be created with a ConstantPoolBuilder to write to class files.

Implementation Note:

Unbound Constant Pool Entries

Implementations may create unbound constant pool entries not belonging to an actual constant pool. They conveniently represent constant pool entries referred by unbound attributes not read from a


class

file. Their index() return a non-positive invalid value, and behaviors of their constantPool() are unspecified. They are considered alien to any contextual constant pool and will be converted when they are written to class files.

Sealed Class Hierarchy Graph:

Since:

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Field Summary

Modifier and Type	Field	Description
`static final int`	`TAG_CLASS`	The tag for `CONSTANT_Class` constant kind.
`static final int`	`TAG_DOUBLE`	The tag for `CONSTANT_Double` constant kind.
`static final int`	`TAG_DYNAMIC`	The tag for `CONSTANT_Dynamic` constant kind.
`static final int`	`TAG_FIELDREF`	The tag for `CONSTANT_Fieldref` constant kind.
`static final int`	`TAG_FLOAT`	The tag for `CONSTANT_Float` constant kind.
`static final int`	`TAG_INTEGER`	The tag for `CONSTANT_Integer` constant kind.
`static final int`	`TAG_INTERFACE_METHODREF`	The tag for `CONSTANT_InterfaceMethodref` constant kind.
`static final int`	`TAG_INVOKE_DYNAMIC`	The tag for `CONSTANT_InvokeDynamic` constant kind.
`static final int`	`TAG_LONG`	The tag for `CONSTANT_Long` constant kind.
`static final int`	`TAG_METHOD_HANDLE`	The tag for `CONSTANT_MethodHandle` constant kind.
`static final int`	`TAG_METHOD_TYPE`	The tag for `CONSTANT_MethodType` constant kind.
`static final int`	`TAG_METHODREF`	The tag for `CONSTANT_Methodref` constant kind.
`static final int`	`TAG_MODULE`	The tag for `CONSTANT_Module` constant kind.
`static final int`	`TAG_NAME_AND_TYPE`	The tag for `CONSTANT_NameAndType` constant kind.
`static final int`	`TAG_PACKAGE`	The tag for `CONSTANT_Package` constant kind.
`static final int`	`TAG_STRING`	The tag for `CONSTANT_String` constant kind.
`static final int`	`TAG_UTF8`	The tag for `CONSTANT_Utf8` constant kind.

Method Summary

Modifier and Type	Method	Description
`ConstantPool`	`constantPool()`	Returns the constant pool this entry is from.
`int`	`index()`	Returns the index within the constant pool corresponding to this entry.
`int`	`tag()`	Returns the constant pool tag that describes the type of this entry.
`int`	`width()`	Returns the number of constant pool slots this entry consumes.

Field Details

TAG_CLASS

static final int TAG_CLASS

The tag for CONSTANT_Class constant kind.

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TAG_DOUBLE

static final int TAG_DOUBLE

The tag for CONSTANT_Double constant kind.

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TAG_DYNAMIC

static final int TAG_DYNAMIC

The tag for CONSTANT_Dynamic constant kind.

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TAG_FIELDREF

static final int TAG_FIELDREF

The tag for CONSTANT_Fieldref constant kind.

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TAG_FLOAT

static final int TAG_FLOAT

The tag for CONSTANT_Float constant kind.

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TAG_INTEGER

static final int TAG_INTEGER

The tag for CONSTANT_Integer constant kind.

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TAG_INTERFACE_METHODREF

static final int TAG_INTERFACE_METHODREF

The tag for CONSTANT_InterfaceMethodref constant kind.

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TAG_INVOKE_DYNAMIC

static final int TAG_INVOKE_DYNAMIC

The tag for CONSTANT_InvokeDynamic constant kind.

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TAG_LONG

static final int TAG_LONG

The tag for CONSTANT_Long constant kind.

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TAG_METHOD_HANDLE

static final int TAG_METHOD_HANDLE

The tag for CONSTANT_MethodHandle constant kind.

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TAG_METHODREF

static final int TAG_METHODREF

The tag for CONSTANT_Methodref constant kind.

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TAG_METHOD_TYPE

static final int TAG_METHOD_TYPE

The tag for CONSTANT_MethodType constant kind.

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TAG_MODULE

static final int TAG_MODULE

The tag for CONSTANT_Module constant kind.

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TAG_NAME_AND_TYPE

static final int TAG_NAME_AND_TYPE

The tag for CONSTANT_NameAndType constant kind.

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TAG_PACKAGE

static final int TAG_PACKAGE

The tag for CONSTANT_Package constant kind.

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TAG_STRING

static final int TAG_STRING

The tag for CONSTANT_String constant kind.

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TAG_UTF8

static final int TAG_UTF8

The tag for CONSTANT_Utf8 constant kind.

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Method Details

constantPool

ConstantPool constantPool()

Returns the constant pool this entry is from.

API Note:

Given a ConstantPoolBuilder builder and a


PoolEntry entry

, use builder.canWriteDirect(entry.constantPool()) instead of object equality of the constant pool to determine if an entry belongs to the builder.

Returns:

the constant pool this entry is from

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tag

int tag()

Returns the constant pool tag that describes the type of this entry.

API Note:: TAG_-prefixed constants in this class, such as TAG_UTF8, describe the possible return values of this method.
Returns:: the constant pool tag that describes the type of this entry

index

int index()

Returns the index within the constant pool corresponding to this entry. A valid index is always positive; if the index is non-positive, this entry is unbound.

Returns:

the index within the constant pool corresponding to this entry

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width

int width()

Returns the number of constant pool slots this entry consumes.

All pool entries except CONSTANT_Long and CONSTANT_Double have width 1. These two exceptions have width 2, and their subsequent indices at index() + 1 are considered unusable.

API Note:

If this entry is loadable, the width of this entry does not decide if this entry should be loaded with ldc or ldc2_w. For example, ConstantDynamicEntry always has width 1, but it must be loaded with ldc2_w if its type is long or double. Use typeKind().slotSize() to determine the loading instruction instead.

Returns:

the number of constant pool slots this entry consumes

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