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 * @version $Id: ConstantString.java 1749603 2016-06-21 20:50:19Z ggregory $ 031 * @see Constant 032 */ 033public final class ConstantString extends Constant implements ConstantObject { 034 035 private int string_index; // Identical to ConstantClass except for this name 036 037 038 /** 039 * Initialize from another object. 040 */ 041 public ConstantString(final ConstantString c) { 042 this(c.getStringIndex()); 043 } 044 045 046 /** 047 * Initialize instance from file data. 048 * 049 * @param file Input stream 050 * @throws IOException 051 */ 052 ConstantString(final DataInput file) throws IOException { 053 this(file.readUnsignedShort()); 054 } 055 056 057 /** 058 * @param string_index Index of Constant_Utf8 in constant pool 059 */ 060 public ConstantString(final int string_index) { 061 super(Const.CONSTANT_String); 062 this.string_index = string_index; 063 } 064 065 066 /** 067 * Called by objects that are traversing the nodes of the tree implicitely 068 * defined by the contents of a Java class. I.e., the hierarchy of methods, 069 * fields, attributes, etc. spawns a tree of objects. 070 * 071 * @param v Visitor object 072 */ 073 @Override 074 public void accept( final Visitor v ) { 075 v.visitConstantString(this); 076 } 077 078 079 /** 080 * Dump constant field reference to file stream in binary format. 081 * 082 * @param file Output file stream 083 * @throws IOException 084 */ 085 @Override 086 public final void dump( final DataOutputStream file ) throws IOException { 087 file.writeByte(super.getTag()); 088 file.writeShort(string_index); 089 } 090 091 092 /** 093 * @return Index in constant pool of the string (ConstantUtf8). 094 */ 095 public final int getStringIndex() { 096 return string_index; 097 } 098 099 100 /** 101 * @param string_index the index into the constant of the string value 102 */ 103 public final void setStringIndex( final int string_index ) { 104 this.string_index = string_index; 105 } 106 107 108 /** 109 * @return String representation. 110 */ 111 @Override 112 public final String toString() { 113 return super.toString() + "(string_index = " + string_index + ")"; 114 } 115 116 117 /** @return String object 118 */ 119 @Override 120 public Object getConstantValue( final ConstantPool cp ) { 121 final Constant c = cp.getConstant(string_index, Const.CONSTANT_Utf8); 122 return ((ConstantUtf8) c).getBytes(); 123 } 124 125 126 /** @return dereferenced string 127 */ 128 public String getBytes( final ConstantPool cp ) { 129 return (String) getConstantValue(cp); 130 } 131}