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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;
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 vars = new HashMap();
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 "$" sign
38       *
39       * @return true if the variable is declared
40       */
41      public boolean isDeclaredVariable(String varName) {
42          return vars.containsKey(varName);
43      }
44  
45      /***
46       * Returns the value of the variable if it is defined,
47       * otherwise, throws IllegalArgumentException
48       *
49       * @param varName is a variable name without the "$" sign
50       *
51       * @return the value of the variable
52       */
53      public Object getVariable(String 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(
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 "$" sign
69       * @param value is the new value for the variable, which can be null
70       */
71      public void declareVariable(String varName, Object value) {
72          vars.put(varName, value);
73      }
74  
75      /***
76       * Removes an existing variable. May throw UnsupportedOperationException.
77       *
78       * @param varName is a variable name without the "$" sign
79       */
80      public void undeclareVariable(String varName) {
81          vars.remove(varName);
82      }
83      
84      public String toString() {
85          return vars.toString();
86      }
87  }