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: package org.apache.commons.scxml.semantics;
18:
19: import java.io.Serializable;
20: import java.util.Comparator;
21:
22: import org.apache.commons.scxml.SCXMLHelper;
23: import org.apache.commons.scxml.model.TransitionTarget;
24:
25: /**
26: * A comparator for TransitionTarget instances.
27: *
28: */
29: final class TransitionTargetComparator implements Comparator,
30: Serializable {
31:
32: /**
33: * Serial version UID.
34: */
35: private static final long serialVersionUID = 1L;
36:
37: /**
38: * Constructor.
39: */
40: TransitionTargetComparator() {
41: super ();
42: }
43:
44: /**
45: * Compares two instances of TransitionTarget in terms of the
46: * SCXML tree hierarchy.
47: * <p>Important Remarks:</p> does not fullfill the Comparator contract,
48: * since it returns 0 if o1 == o2 and also if they are not related to each
49: * other and at the same time the chain-to-parent length for o1 is the
50: * same length as for o2 (that is, they are equally deeply nested)
51: *
52: * @param o1 The first TransitionTarget object
53: * @param o2 The second TransitionTarget object
54: * @return int The comparation result
55: * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
56: * @see TransitionTarget
57: */
58: public int compare(final Object o1, final Object o2) {
59: TransitionTarget tt1 = (TransitionTarget) o1;
60: TransitionTarget tt2 = (TransitionTarget) o2;
61: if (tt1 == tt2) {
62: return 0;
63: } else if (SCXMLHelper.isDescendant(tt1, tt2)) {
64: return -1;
65: } else if (SCXMLHelper.isDescendant(tt2, tt1)) {
66: return 1;
67: } else {
68: //the tt1 and tt2 are parallel, now we have to count chain sizes
69: int tc1 = countChainLength(tt1);
70: int tc2 = countChainLength(tt2);
71: //longer the chain, deeper the node is
72: return tc2 - tc1;
73: }
74: }
75:
76: /**
77: * The "depth" at which this TransitionTarget exists in the
78: * SCXML object model.
79: *
80: * @param tt The TransitionTarget
81: * @return int The "depth"
82: */
83: private int countChainLength(final TransitionTarget tt) {
84: int count = 0;
85: TransitionTarget parent = tt.getParent();
86: while (parent != null) {
87: count++;
88: parent = parent.getParent();
89: }
90: return count;
91: }
92: }
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