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=== Java ===
Java supports [[Thread pool pattern|thread pooling]] via <code>java.util.concurrent.ExecutorService</code> and other related classes. The executor service has a certain number of "basic" threads that are never discarded. If all threads are busy, the service allocates the allowed number of extra threads that are later discarded if not used for the certain expiration time. If no more threads are allowed, the tasks can be placed in the queue. Finally, if this queue may get too long, it can be configured to suspend the requesting thread.
<syntaxhighlight lang="java">
public class PooledObject {
public String temp1;
public String temp2;
public String temp3;
public String getTemp1() {
return temp1;
}
public void setTemp1(String temp1) {
this.temp1 = temp1;
}
public String getTemp2() {
return temp2;
}
public void setTemp2(String temp2) {
this.temp2 = temp2;
}
public String getTemp3() {
return temp3;
}
public void setTemp3(String temp3) {
this.temp3 = temp3;
}
}
</syntaxhighlight><syntaxhighlight lang="java">
public class PooledObjectPool {
private static long expTime = 60000;//6 seconds
public static HashMap<PooledObject, Long> available = new HashMap<PooledObject, Long>();
public static HashMap<PooledObject, Long> inUse = new HashMap<PooledObject, Long>();
public synchronized static PooledObject getObject() {
long now = System.currentTimeMillis();
if (available.isEmpty()) {
PooledObject po = new PooledObject();
push(inUse, po, now);
return po;
} else {
for (Map.Entry<PooledObject, Long> entry : available.entrySet()) {
if (now - entry.getValue() > expTime) { //object has expired
popElement(available);
} else {
PooledObject po = popElement(available, entry.getKey());
cleanUp(po);
push(inUse, po, now);
return po;
}
}
}
return null;
}
private synchronized static void push(HashMap<PooledObject, Long> map,
PooledObject po, long now) {
map.put(po, now);
}
public static void releaseObject(PooledObject po) {
cleanUp(po);
available.put(po, System.currentTimeMillis());
inUse.remove(po);
}
public static PooledObject popElement(HashMap<PooledObject, Long> map) {
Map.Entry<PooledObject, Long> entry = map.entrySet().iterator().next();
PooledObject key= entry.getKey();
//Long value=entry.getValue();
map.remove(entry.getKey());
return key;
}
public static PooledObject popElement(HashMap<PooledObject, Long> map, PooledObject key) {
map.remove(key);
return key;
}
public static void cleanUp(PooledObject po) {
po.setTemp1(null);
po.setTemp2(null);
po.setTemp3(null);
}
}
</syntaxhighlight>
== See also ==
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