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Java > Open Source Codes > org > apache > bcel > classfile > ConstantString


1 /*
2  * Copyright 2000-2004 The Apache Software Foundation
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  *
16  */
17 package org.apache.bcel.classfile;
18
19 import java.io.DataInputStream JavaDoc;
20 import java.io.DataOutputStream JavaDoc;
21 import java.io.IOException JavaDoc;
22 import org.apache.bcel.Constants;
23
24 /**
25  * This class is derived from the abstract
26  * <A HREF="org.apache.bcel.classfile.Constant.html">Constant</A> class
27  * and represents a reference to a String object.
28  *
29  * @version $Id: ConstantString.java 386056 2006-03-15 11:31:56Z tcurdt $
30  * @author <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
31  * @see Constant
32  */
33 public final class ConstantString extends Constant implements ConstantObject {
34
35     private int string_index; // Identical to ConstantClass except for this name
36
37
38     /**
39      * Initialize from another object.
40      */
41     public ConstantString(ConstantString c) {
42         this(c.getStringIndex());
43     }
44
45
46     /**
47      * Initialize instance from file data.
48      *
49      * @param file Input stream
50      * @throws IOException
51      */
52     ConstantString(DataInputStream JavaDoc file) throws IOException JavaDoc {
53         this(file.readUnsignedShort());
54     }
55
56
57     /**
58      * @param string_index Index of Constant_Utf8 in constant pool
59      */
60     public ConstantString(int string_index) {
61         super(Constants.CONSTANT_String);
62         this.string_index = string_index;
63     }
64
65
66     /**
67      * Called by objects that are traversing the nodes of the tree implicitely
68      * defined by the contents of a Java class. I.e., the hierarchy of methods,
69      * fields, attributes, etc. spawns a tree of objects.
70      *
71      * @param v Visitor object
72      */
73     public void accept( Visitor v ) {
74         v.visitConstantString(this);
75     }
76
77
78     /**
79      * Dump constant field reference to file stream in binary format.
80      *
81      * @param file Output file stream
82      * @throws IOException
83      */
84     public final void dump( DataOutputStream JavaDoc file ) throws IOException JavaDoc {
85         file.writeByte(tag);
86         file.writeShort(string_index);
87     }
88
89
90     /**
91      * @return Index in constant pool of the string (ConstantUtf8).
92      */
93     public final int getStringIndex() {
94         return string_index;
95     }
96
97
98     /**
99      * @param string_index the index into the constant of the string value
100      */
101     public final void setStringIndex( int string_index ) {
102         this.string_index = string_index;
103     }
104
105
106     /**
107      * @return String representation.
108      */
109     public final String JavaDoc toString() {
110         return super.toString() + "(string_index = " + string_index + ")";
111     }
112
113
114     /** @return String object
115      */
116     public Object JavaDoc getConstantValue( ConstantPool cp ) {
117         Constant c = cp.getConstant(string_index, Constants.CONSTANT_Utf8);
118         return ((ConstantUtf8) c).getBytes();
119     }
120
121
122     /** @return dereferenced string
123      */
124     public String JavaDoc getBytes( ConstantPool cp ) {
125         return (String JavaDoc) getConstantValue(cp);
126     }
127 }
128
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