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1
2 package org.objectweb.jac.util;
3
4 import java.lang.ref.Reference  ;
5 import java.lang.ref.ReferenceQueue ;
6 import java.lang.ref.WeakReference ;
7 import java.util.AbstractList ;
8 import java.util.ArrayList ;
9 import java.util.List ;
10 import org.apache.log4j.Logger;
11
12 public class WeakList extends AbstractList {
13 static Logger logger = Logger.getLogger("weak.collections");
14
15
18 private final ReferenceQueue queue = new ReferenceQueue ();
19
20 private final List list=new ArrayList ();
21
22 public boolean add(Object o) {
23 expungeStaleEntries();
24 return list.add(new ListEntry(o,queue));
25 }
26
27 public Object get(int i) {
28 expungeStaleEntries();
29 return ((Reference )list.get(i)).get();
30 }
31
32 public int size() {
33 expungeStaleEntries();
35 return list.size();
36 }
37
38 public Object remove(int index) {
39 return ((ListEntry)list.remove(index)).get();
40 }
41
42
45 private void expungeStaleEntries() {
46 Object r;
47 while ( (r = queue.poll()) != null) {
48 ListEntry e = (ListEntry)r;
49 int i=list.indexOf(r);
50 if(i!=-1) {
51 logger.debug("removing from list "+r+" ("+i+")");
52 list.remove(i);
53 }
54 }
55 }
56
57 private static class ListEntry extends WeakReference {
58 String objectString;
59 public ListEntry(Object o,ReferenceQueue queue) {
60 super(o,queue);
61 objectString=o.toString();
62 }
63 public boolean equals(Object o) {
64 if(o==null) {
65 return false;
66 } else {
67 if((o instanceof ListEntry)) {
68 return o.hashCode()==this.hashCode();
69 } else {
70 if(this.get()==null) return false;
71 return this.get().equals(o);
72 }
73 }
74 }
75 public String toString() {
76 if(this.get()==null) {
77 return "'entry "+objectString+" <GARBAGED>'";
78 } else {
79 return "'entry "+this.get()+"'";
80 }
81 }
82
83 }
84 }
85 |
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