Package org.apache.bcel.classfile

Class ConstantPool

java.lang.Object

org.apache.bcel.classfile.ConstantPool

All Implemented Interfaces:

java.lang.Cloneable, java.lang.Iterable<Constant>, Node

public class ConstantPool
extends java.lang.Object
implements java.lang.Cloneable, Node, java.lang.Iterable<Constant>

This class represents the constant pool, that is, a table of constants, of a parsed classfile. It may contain null references, due to the JVM specification that skips an entry after an 8-byte constant (double, long) entry. Those interested in generating constant pools programmatically should see ConstantPoolGen.

See Also:

Constant, ConstantPoolGen

Constructor Summary

Constructors

Constructor	Description
ConstantPool(java.io.DataInput input)	Reads constants from given input stream.
ConstantPool(Constant... constantPool)	Constructs a ConstantPool.

Method Summary

Modifier and Type	Method	Description
void	accept(Visitor v)	Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
java.lang.String	constantToString(int index, byte tag)	Retrieves constant at 'index' from constant pool and resolve it to a string representation.
java.lang.String	constantToString(Constant c)	Resolves constant to a string representation.
ConstantPool	copy()	Creates a deep copy of this constant pool.
void	dump(java.io.DataOutputStream file)	Dumps constant pool to file stream in binary format.
<T extends Constant> T	getConstant(int index)	Gets constant from constant pool.
<T extends Constant> T	getConstant(int index, byte tag)	Gets constant from constant pool and check whether it has the expected type.
<T extends Constant> T	getConstant(int index, byte tag, java.lang.Class<T> castTo)	Gets constant from constant pool and check whether it has the expected type.
<T extends Constant> T	getConstant(int index, java.lang.Class<T> castTo)	Gets constant from constant pool.
ConstantInteger	getConstantInteger(int index)	Gets constant from constant pool and check whether it has the expected type.
Constant[]	getConstantPool()	Gets the array of constants.
java.lang.String	getConstantString(int index, byte tag)	Gets string from constant pool and bypass the indirection of 'ConstantClass' and 'ConstantString' objects.
ConstantUtf8	getConstantUtf8(int index)	Gets constant from constant pool and check whether it has the expected type.
int	getLength()	Gets the length of constant pool.
java.util.Iterator<Constant>	iterator()
void	setConstant(int index, Constant constant)	Sets a constant at the specified index.
void	setConstantPool(Constant[] constantPool)	Sets the constant pool.
java.lang.String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Constructor Detail

ConstantPool

public ConstantPool(Constant... constantPool)

Constructs a ConstantPool.

Parameters:

constantPool - Array of constants.

ConstantPool

public ConstantPool(java.io.DataInput input)
             throws java.io.IOException

Reads constants from given input stream.

Parameters:

input - Input stream.

Throws:

java.io.IOException - Thrown if problem in readUnsignedShort or readConstant.

Method Detail

accept

public void accept(Visitor v)

Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class. I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.

Specified by:

accept in interface Node

Parameters:

v - Visitor object.

constantToString

public java.lang.String constantToString(Constant c)
                                  throws java.lang.IllegalArgumentException

Resolves constant to a string representation.

Parameters:

c - Constant to be printed.

Returns:

String representation.

Throws:

java.lang.IllegalArgumentException - Thrown if c is unknown constant type.

constantToString

public java.lang.String constantToString(int index,
                                         byte tag)

Retrieves constant at 'index' from constant pool and resolve it to a string representation.

Parameters:

index - of constant in constant pool.

tag - expected type.

Returns:

String representation.

copy

public ConstantPool copy()

Creates a deep copy of this constant pool.

Returns:

deep copy of this constant pool.

dump

public void dump(java.io.DataOutputStream file)
          throws java.io.IOException

Dumps constant pool to file stream in binary format.

Parameters:

file - Output file stream.

Throws:

java.io.IOException - Thrown if problem in writeShort or dump

getConstant

public <T extends Constant> T getConstant(int index)
                                   throws ClassFormatException

Gets constant from constant pool.

Type Parameters:

T - The type of the constant.

Parameters:

index - Index in constant pool.

Returns:

Constant value.

Throws:

ClassFormatException - Thrown if index is invalid.

See Also:

Constant

getConstant

public <T extends Constant> T getConstant(int index,
                                          byte tag)
                                   throws ClassFormatException

Gets constant from constant pool and check whether it has the expected type.

Type Parameters:

T - The type of the constant.

Parameters:

index - Index in constant pool.

tag - Tag of expected constant, that is, its type.

Returns:

Constant value.

Throws:

ClassFormatException - Thrown if constant type does not match tag.

See Also:

Constant

getConstant

public <T extends Constant> T getConstant(int index,
                                          byte tag,
                                          java.lang.Class<T> castTo)
                                   throws ClassFormatException

Gets constant from constant pool and check whether it has the expected type.

Type Parameters:

T - The type of the constant.

Parameters:

index - Index in constant pool.

tag - Tag of expected constant, that is, its type.

castTo - The class to cast to.

Returns:

Constant value.

Throws:

ClassFormatException - Thrown if constant type does not match tag.

Since:

6.6.0

See Also:

Constant

getConstant

public <T extends Constant> T getConstant(int index,
                                          java.lang.Class<T> castTo)
                                   throws ClassFormatException

Gets constant from constant pool.

Type Parameters:

T - A Constant subclass.

Parameters:

index - Index in constant pool.

castTo - The Constant subclass to cast to.

Returns:

Constant value.

Throws:

ClassFormatException - Thrown if index is invalid.

Since:

6.6.0

See Also:

Constant

getConstantInteger

public ConstantInteger getConstantInteger(int index)

Gets constant from constant pool and check whether it has the expected type.

Parameters:

index - Index in constant pool.

Returns:

ConstantInteger value.

Throws:

ClassFormatException - Thrown if constant type does not match tag.

See Also:

ConstantInteger

getConstantPool

public Constant[] getConstantPool()

Gets the array of constants.

Returns:

Array of constants.

See Also:

Constant

getConstantString

public java.lang.String getConstantString(int index,
                                          byte tag)
                                   throws java.lang.IllegalArgumentException

Gets string from constant pool and bypass the indirection of 'ConstantClass' and 'ConstantString' objects. I.e. these classes have an index field that points to another entry of the constant pool of type 'ConstantUtf8' which contains the real data.

Parameters:

index - Index in constant pool.

tag - Tag of expected constant, either ConstantClass or ConstantString.

Returns:

Contents of string reference.

Throws:

java.lang.IllegalArgumentException - Thrown if tag is invalid.

See Also:

ConstantClass, ConstantString

getConstantUtf8

public ConstantUtf8 getConstantUtf8(int index)
                             throws ClassFormatException

Gets constant from constant pool and check whether it has the expected type.

Parameters:

index - Index in constant pool.

Returns:

ConstantUtf8 value.

Throws:

ClassFormatException - Thrown if constant type does not match tag.

See Also:

ConstantUtf8

getLength

public int getLength()

Gets the length of constant pool.

Returns:

Length of constant pool.

iterator

public java.util.Iterator<Constant> iterator()

Specified by:

iterator in interface java.lang.Iterable<Constant>

setConstant

public void setConstant(int index,
                        Constant constant)

Sets a constant at the specified index.

Parameters:

index - The index in the constant pool.

constant - Constant to set.

setConstantPool

public void setConstantPool(Constant[] constantPool)

Sets the constant pool.

Parameters:

constantPool - The constant pool array.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

Returns:

String representation.