01: /*
02: * Licensed to the Apache Software Foundation (ASF) under one or more
03: * contributor license agreements. See the NOTICE file distributed with
04: * this work for additional information regarding copyright ownership.
05: * The ASF licenses this file to You under the Apache License, Version 2.0
06: * (the "License"); you may not use this file except in compliance with
07: * the License. You may obtain a copy of the License at
08: *
09: * http://www.apache.org/licenses/LICENSE-2.0
10: *
11: * Unless required by applicable law or agreed to in writing, software
12: * distributed under the License is distributed on an "AS IS" BASIS,
13: * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14: * See the License for the specific language governing permissions and
15: * limitations under the License.
16: *
17: */
18: package org.apache.tools.ant.taskdefs.condition;
19:
20: import org.apache.tools.ant.BuildException;
21:
22: import java.util.Enumeration;
23:
24: /**
25: * The <tt>Xor</tt> condition type to exclusive or operations.
26: * This does not shortcut stuff.
27: */
28: public class Xor extends ConditionBase implements Condition {
29:
30: /**
31: * Evaluate the contained conditions.
32: * @return the result of xoring the conditions together.
33: * @throws org.apache.tools.ant.BuildException
34: * if an error occurs.
35: */
36: public boolean eval() throws BuildException {
37: Enumeration e = getConditions();
38: //initial state is false.
39: boolean state = false;
40: while (e.hasMoreElements()) {
41: Condition c = (Condition) e.nextElement();
42: //every condition is xored against the previous one
43: state ^= c.eval();
44: }
45: return state;
46: }
47:
48: }
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