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19
20 package org.apache.cayenne.graph;
21
22 /**
23  * An abstract superclass of operations on individual nodes and arcs in a digraph.
24  *
25  * @since 1.2
26  * @author Andrus Adamchik
27  */
28 public abstract class NodeDiff implements GraphDiff, Comparable JavaDoc {
29
30     protected int diffId;
31     protected Object JavaDoc nodeId;
32
33     public NodeDiff(Object JavaDoc nodeId) {
34         this.nodeId = nodeId;
35     }
36
37     public NodeDiff(Object JavaDoc nodeId, int diffId) {
38         this.nodeId = nodeId;
39         this.diffId = diffId;
40     }
41
42     public boolean isNoop() {
43         return false;
44     }
45
46     public abstract void apply(GraphChangeHandler tracker);
47
48     public abstract void undo(GraphChangeHandler tracker);
49
50     public Object JavaDoc getNodeId() {
51         return nodeId;
52     }
53
54     /**
55      * Returns an id of this diff that can be used for various purposes, such as
56      * identifying the order of the diff in a sequence.
57      */
58     public int getDiffId() {
59         return diffId;
60     }
61
62     /**
63      * Sets an id of this diff that can be used for various purposes, such as identifying
64      * the order of the diff in a sequence.
65      */
66     public void setDiffId(int diffId) {
67         this.diffId = diffId;
68     }
69
70     /**
71      * Implements a Comparable interface method to compare based on diffId property.
72      */
73     public int compareTo(Object JavaDoc o) {
74         if (!(o instanceof NodeDiff)) {
75             throw new IllegalArgumentException JavaDoc("Can't compare to " + o);
76         }
77
78         return diffId - ((NodeDiff) o).getDiffId();
79     }
80 }
81
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