Class ConstantPool

java.lang.Object
org.apache.bcel.classfile.ConstantPool
All Implemented Interfaces:
Cloneable, Iterable<Constant>, Node
public class ConstantPool extends Object implements Cloneable, Node, 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:

  • Constructor Details

    • ConstantPool

      public ConstantPool(Constant... constantPool)
      Constructs a ConstantPool.
      Parameters:
      constantPool - Array of constants.

    • ConstantPool

      public ConstantPool(DataInput input) throws IOException
      Reads constants from given input stream.
      Parameters:
      input - Input stream.
      Throws:
      IOException - if problem in readUnsignedShort or readConstant.

  • Method Details

    • 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 String constantToString(Constant c) throws IllegalArgumentException
      Resolves constant to a string representation.
      Parameters:
      c - Constant to be printed.
      Returns:
      String representation.
      Throws:
      IllegalArgumentException - if c is unknown constant type.

    • constantToString

      public 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(DataOutputStream file) throws IOException
      Dumps constant pool to file stream in binary format.
      Parameters:
      file - Output file stream.
      Throws:
      IOException - 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 - if index is invalid.
      See Also:

    • 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 - if constant type does not match tag.
      See Also:

    • getConstant

      public <T extends Constant> T getConstant(int index, byte tag, 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 - if constant type does not match tag.
      Since:
      6.6.0
      See Also:

    • getConstant

      public <T extends Constant> T getConstant(int index, 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 - if index is invalid.
      Since:
      6.6.0
      See Also:

    • 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 - if constant type does not match tag.
      See Also:

    • getConstantPool

      public Constant[] getConstantPool()
      Gets the array of constants.
      Returns:
      Array of constants.
      See Also:

    • getConstantString

      public String getConstantString(int index, byte tag) throws 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:
      IllegalArgumentException - if tag is invalid.
      See Also:

    • 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 - if constant type does not match tag.
      See Also:

    • getLength

      public int getLength()
      Gets the length of constant pool.
      Returns:
      Length of constant pool.

    • iterator

      public Iterator<Constant> iterator()
      Specified by:
      iterator in interface 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 String toString()
      Overrides:
      toString in class Object
      Returns:
      String representation.