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 */ 017package org.apache.bcel.classfile; 018 019import java.io.DataInput; 020import java.io.DataOutputStream; 021import java.io.IOException; 022 023import org.apache.bcel.Const; 024 025/** 026 * This class is derived from the abstract {@link Constant} and represents a reference to a (external) class. 027 * 028 * @see Constant 029 */ 030public final class ConstantClass extends Constant implements ConstantObject { 031 032 private int nameIndex; // Identical to ConstantString except for the name 033 034 /** 035 * Initialize from another object. 036 */ 037 public ConstantClass(final ConstantClass c) { 038 this(c.getNameIndex()); 039 } 040 041 /** 042 * Constructs an instance from file data. 043 * 044 * @param dataInput Input stream 045 * @throws IOException if an I/O error occurs reading from the given {@code dataInput}. 046 */ 047 ConstantClass(final DataInput dataInput) throws IOException { 048 this(dataInput.readUnsignedShort()); 049 } 050 051 /** 052 * @param nameIndex Name index in constant pool. Should refer to a ConstantUtf8. 053 */ 054 public ConstantClass(final int nameIndex) { 055 super(Const.CONSTANT_Class); 056 this.nameIndex = nameIndex; 057 } 058 059 /** 060 * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class. 061 * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects. 062 * 063 * @param v Visitor object 064 */ 065 @Override 066 public void accept(final Visitor v) { 067 v.visitConstantClass(this); 068 } 069 070 /** 071 * Dumps constant class to file stream in binary format. 072 * 073 * @param file Output file stream 074 * @throws IOException if an I/O error occurs writing to the DataOutputStream. 075 */ 076 @Override 077 public void dump(final DataOutputStream file) throws IOException { 078 file.writeByte(super.getTag()); 079 file.writeShort(nameIndex); 080 } 081 082 /** 083 * @return dereferenced string 084 */ 085 public String getBytes(final ConstantPool cp) { 086 return (String) getConstantValue(cp); 087 } 088 089 /** 090 * @return String object 091 */ 092 @Override 093 public Object getConstantValue(final ConstantPool cp) { 094 return cp.getConstantUtf8(nameIndex).getBytes(); 095 } 096 097 /** 098 * @return Name index in constant pool of class name. 099 */ 100 public int getNameIndex() { 101 return nameIndex; 102 } 103 104 /** 105 * @param nameIndex the name index in the constant pool of this Constant Class 106 */ 107 public void setNameIndex(final int nameIndex) { 108 this.nameIndex = nameIndex; 109 } 110 111 /** 112 * @return String representation. 113 */ 114 @Override 115 public String toString() { 116 return super.toString() + "(nameIndex = " + nameIndex + ")"; 117 } 118}