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Java > Open Source Codes > org > mr > api > jms > selector > syntax > UnaryMinus


1 /*
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16  * The Original Code is "MantaRay" (TM).
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46 package org.mr.api.jms.selector.syntax;
47
48 import javax.jms.Message JavaDoc;
49
50
51 /**
52  * This class implements a unary minus operator.
53  *
54  */

55 class UnaryMinus extends UnaryOperator {
56
57     /**
58      * The expression context, for error reporting purposes
59      */

60     private static final String JavaDoc CONTEXT = "unary minus";
61
62     /**
63      * Helper for -1
64      */

65     private static final MantaLong MINUS1 = new MantaLong(-1);
66
67     /**
68      * Construct a new UnaryMinus operator
69      *
70      * @param operand the operand
71      */

72     public UnaryMinus(final Expression operand) {
73         super("-", operand);
74     }//UnaryMinus
75

76     
77     /**
78      * Evaluate the expression
79      *
80      * @param msg the message to evaluate this expression against
81      * @return the result of expression
82      * @throws TypeMismatchException if the operand doesn't evaluate to
83      * a numeric or null
84      */

85     public final MantaObject evaluate(final Message JavaDoc msg) throws TypeMismatchException {
86         MantaObject result = null;
87         MantaNumber value = TypeCaster.castToNumber(operand().evaluate(msg),CONTEXT);
88         
89         if (value != null) {
90             result = value.multiply(MINUS1);
91         }//if
92
return result;
93     }//evaluate
94
}//UnaryMinus
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