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Java > Open Source Codes > org > apache > commons > jxpath > BasicVariables


1 /*
2  * Copyright 1999-2004 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 package org.apache.commons.jxpath;
17
18 import java.util.HashMap JavaDoc;
19
20 /**
21  * A basic implementation of the Variables interface that uses a HashMap.
22  *
23  * @author Dmitri Plotnikov
24  * @version $Revision: 1.7 $ $Date: 2004/02/29 14:17:42 $
25  */
26 public class BasicVariables implements Variables {
27
28     /**
29      * Contains the values of declared variables
30      */
31     private HashMap JavaDoc vars = new HashMap JavaDoc();
32
33     /**
34      * Returns true if the variable has been defined, even if the
35      * value of the variable is null.
36      *
37      * @param varName is a variable name without the "$" sign
38      *
39      * @return true if the variable is declared
40      */
41     public boolean isDeclaredVariable(String JavaDoc varName) {
42         return vars.containsKey(varName);
43     }
44
45     /**
46      * Returns the value of the variable if it is defined,
47      * otherwise, throws IllegalArgumentException
48      *
49      * @param varName is a variable name without the "$" sign
50      *
51      * @return the value of the variable
52      */
53     public Object JavaDoc getVariable(String JavaDoc varName) {
54         // Note that a variable may be defined with a null value
55
56         if (vars.containsKey(varName)) {
57             return vars.get(varName);
58         }
59
60         throw new IllegalArgumentException JavaDoc(
61             "No such variable: '" + varName + "'");
62     }
63
64     /**
65      * Defines a new variable with the specified value or modifies
66      * the value of an existing variable.
67      *
68      * @param varName is a variable name without the "$" sign
69      * @param value is the new value for the variable, which can be null
70      */
71     public void declareVariable(String JavaDoc varName, Object JavaDoc value) {
72         vars.put(varName, value);
73     }
74
75     /**
76      * Removes an existing variable. May throw UnsupportedOperationException.
77      *
78      * @param varName is a variable name without the "$" sign
79      */
80     public void undeclareVariable(String JavaDoc varName) {
81         vars.remove(varName);
82     }
83     
84     public String JavaDoc toString() {
85         return vars.toString();
86     }
87 }
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