You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
69 lines
1.4 KiB
69 lines
1.4 KiB
/** From Section 12.5.3, Reference Queues page 324-326
|
|
of 'The Java Programming Language, Third Edition'.
|
|
|
|
But why wasn't it included in the java.util Collection package?
|
|
*/
|
|
|
|
|
|
package org.trinitydesktop.qt;
|
|
|
|
import java.lang.ref.*;
|
|
import java.util.*;
|
|
|
|
public class WeakValueMap extends HashMap {
|
|
private ReferenceQueue reaped = new ReferenceQueue();
|
|
|
|
private static class ValueRef extends WeakReference {
|
|
private final Object key; // key for value
|
|
|
|
ValueRef(Object val, Object key, ReferenceQueue q) {
|
|
super(val, q);
|
|
this.key = key;
|
|
}
|
|
}
|
|
|
|
public Object put(Object key, Object value) {
|
|
reap();
|
|
ValueRef vr = new ValueRef(value, key, reaped);
|
|
return super.put(key, vr);
|
|
}
|
|
|
|
public Object get(Object key) {
|
|
reap();
|
|
ValueRef vr = (ValueRef) super.get(key);
|
|
if (vr == null) {
|
|
return null;
|
|
} else {
|
|
return vr.get();
|
|
}
|
|
}
|
|
|
|
/** Force an entry to be removed if it is known to be invalid,
|
|
rather than waiting for the garbage collector to put it
|
|
on the reaped queue.
|
|
*/
|
|
public Object remove(Object key) {
|
|
reap();
|
|
ValueRef vr = (ValueRef) super.get(key);
|
|
if (vr == null) {
|
|
return null;
|
|
} else {
|
|
vr.clear();
|
|
super.remove(key);
|
|
return null;
|
|
}
|
|
}
|
|
|
|
public int size() {
|
|
reap();
|
|
return super.size();
|
|
}
|
|
|
|
public void reap() {
|
|
ValueRef ref;
|
|
while ((ref = (ValueRef) reaped.poll()) != null) {
|
|
super.remove(ref.key);
|
|
}
|
|
}
|
|
}
|