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Java > Open Source Codes > edu > rice > cs > util > OrderedBidirectionalHashMap


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33
34 package edu.rice.cs.util;
35 import java.util.*;
36
37 public class OrderedBidirectionalHashMap<Type1, Type2> extends BidirectionalHashMap<Type1, Type2> {
38   private ArrayList<Type2> order = new ArrayList<Type2>();
39   
40   public OrderedBidirectionalHashMap() { super(); }
41   
42   public void put(Type1 key, Type2 value) {
43     super.put(key, value);
44     order.add(value);
45   }
46    
47   public Type2 removeValue(Type1 key) {
48     Type2 value = super.removeValue(key);
49     order.remove(value);
50     return value;
51   }
52   
53   public Type1 removeKey(Type2 value) {
54     Type1 key = super.removeKey(value);
55     order.remove(value);
56     return key;
57   }
58   
59   public Iterator<Type2> valuesIterator() { return new OBHMIterator(); }
60   
61   public Collection<Type2> values() { return order; }
62   
63   public void clear() {
64     super.clear();
65     order.clear();
66   }
67   
68     /** Iterator class for BiDirectionalHashMap */
69   class OBHMIterator implements Iterator<Type2> {
70     
71     Iterator<Type2> it = order.iterator();
72 // OrderedBidirectionalHashMap<Type1,Type2> OBHMthis = OrderedBidirectionalHashMap.this;
73
74     /** Cached values of last key and value visited */
75     Type1 lastKey = null;
76     Type2 lastValue = null;
77
78     public boolean hasNext() { return it.hasNext(); }
79     
80     public Type2 next() {
81       lastValue = it.next();
82       return lastValue;
83     }
84     
85     /** Removes last element returned by next(); throws IllegalStateException if no such element */
86     public void remove() {
87       it.remove(); /* throws exception if lastValue is null */
88       lastKey = backward.get(lastValue);
89       forward.remove(lastKey); /* cannot fail because lastKey is not null */
90       backward.remove(lastValue); /* cannot fail because lastValue is not null */
91       lastValue = null;
92     }
93   }
94 }
95
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