001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 * 017 */ 018package org.apache.bcel.classfile; 019 020import java.io.DataInput; 021import java.io.DataOutputStream; 022import java.io.IOException; 023 024import org.apache.bcel.Const; 025 026/** 027 * This class is derived from the abstract {@link Constant} 028 * and represents a reference to a String object. 029 * 030 * @see Constant 031 */ 032public final class ConstantString extends Constant implements ConstantObject { 033 034 private int string_index; // Identical to ConstantClass except for this name 035 036 037 /** 038 * Initialize from another object. 039 */ 040 public ConstantString(final ConstantString c) { 041 this(c.getStringIndex()); 042 } 043 044 045 /** 046 * Initialize instance from file data. 047 * 048 * @param file Input stream 049 * @throws IOException 050 */ 051 ConstantString(final DataInput file) throws IOException { 052 this(file.readUnsignedShort()); 053 } 054 055 056 /** 057 * @param string_index Index of Constant_Utf8 in constant pool 058 */ 059 public ConstantString(final int string_index) { 060 super(Const.CONSTANT_String); 061 this.string_index = string_index; 062 } 063 064 065 /** 066 * Called by objects that are traversing the nodes of the tree implicitely 067 * defined by the contents of a Java class. I.e., the hierarchy of methods, 068 * fields, attributes, etc. spawns a tree of objects. 069 * 070 * @param v Visitor object 071 */ 072 @Override 073 public void accept( final Visitor v ) { 074 v.visitConstantString(this); 075 } 076 077 078 /** 079 * Dump constant field reference to file stream in binary format. 080 * 081 * @param file Output file stream 082 * @throws IOException 083 */ 084 @Override 085 public void dump( final DataOutputStream file ) throws IOException { 086 file.writeByte(super.getTag()); 087 file.writeShort(string_index); 088 } 089 090 091 /** 092 * @return Index in constant pool of the string (ConstantUtf8). 093 */ 094 public int getStringIndex() { 095 return string_index; 096 } 097 098 099 /** 100 * @param string_index the index into the constant of the string value 101 */ 102 public void setStringIndex( final int string_index ) { 103 this.string_index = string_index; 104 } 105 106 107 /** 108 * @return String representation. 109 */ 110 @Override 111 public String toString() { 112 return super.toString() + "(string_index = " + string_index + ")"; 113 } 114 115 116 /** @return String object 117 */ 118 @Override 119 public Object getConstantValue( final ConstantPool cp ) { 120 final Constant c = cp.getConstant(string_index, Const.CONSTANT_Utf8); 121 return ((ConstantUtf8) c).getBytes(); 122 } 123 124 125 /** @return dereferenced string 126 */ 127 public String getBytes( final ConstantPool cp ) { 128 return (String) getConstantValue(cp); 129 } 130}