NegationOperation


1   package org.jicengine.operation;
2   
3   /**
4    * <p> </p>
5    *
6    * <p> </p>
7    *
8    * <p> </p>
9    *
10   * <p> </p>
11   *
12   * @author timo laitinen
13   */
14  public class NegationOperation implements Operation {
15      private Operation operation;
16      public NegationOperation(Operation operation)
17      {
18          this.operation = operation;
19      }
20  
21      /**
22       * <p> executes the operation in a given context.
23       *
24       * @param context Context
25       * @throws OperationException
26       * @return Object
27       */
28      public Object   execute(Context context) throws OperationException
29      {
30          Object   result = this.operation.execute(context);
31          if( result == null ){
32              // null means true to here.
33              return Boolean.TRUE;
34          }
35          else if( result instanceof Boolean   ){
36              // negate the boolean
37              return new Boolean  (!((Boolean  )result).booleanValue());
38          }
39          else {
40              // non-null, non-boolean means false
41              return Boolean.FALSE;
42          }
43  
44      }
45  
46      /**
47       * <p> So clients may query if this operation needs a particular parameter.
48       *
49       * @param name String
50       * @return boolean
51       */
52      public boolean needsParameter(String   name)
53      {
54          return this.operation.needsParameter(name);
55      }
56  
57      /**
58       * So clients may query whether this operation needs any parameters at all.
59       *
60       * @return boolean
61       */
62      public boolean needsParameters()
63      {
64          return this.operation.needsParameters();
65      }
66  }
67
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