Package org.apache.bcel.classfile

Class 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, i.e., 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)  

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      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()  
      void dump​(java.io.DataOutputStream file)
      Dump 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()  
      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()  
      java.util.Iterator<Constant> iterator()  
      void setConstant​(int index, Constant constant)  
      void setConstantPool​(Constant[] constantPool)  
      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)
        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 - 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 - 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

      • dump

        public void dump​(java.io.DataOutputStream file)
          throws java.io.IOException
        Dump constant pool to file stream in binary format.
        Parameters:
        file - Output file stream
        Throws:
        java.io.IOException - if problem in writeShort or dump

      • 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.
        Parameters:
        index - Index in constant pool
        tag - Tag of expected constant, i.e., its type
        Returns:
        Constant value
        Throws:
        ClassFormatException - 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.
        Parameters:
        index - Index in constant pool
        tag - Tag of expected constant, i.e., its type
        Returns:
        Constant value
        Throws:
        ClassFormatException - if constant type does not match tag
        Since:
        6.6.0
        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 - if tag is invalid
        See Also:
        ConstantClass, ConstantString

      • getLength

        public int getLength()
        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)
        Parameters:
        constant - Constant to set

      • toString

        public java.lang.String toString()
        Overrides:
        toString in class java.lang.Object
        Returns:
        String representation.