问大家如何设计对象池？

get()从池中获取对象
free()把对象还回池中
clear()清洗池
getObjectCount()获取池中存在的对象数目
getActiveObjectCount()获取目前在池外工作的对象数目
elements()获取池中所有对象的数组

package huzq.Pools;

import java.util.*;

public abstract class Pool{
private Vector buffer;

private int objectCount;
private int maxObject;

public Pool(int maxObject){
this.maxObject = maxObject;
objectCount = 0;
buffer = new Vector(maxObject);
}

protected abstract Object creat();
protected abstract void close(Object obj);

private Object _get(){
Object obj = null;
if (buffer.isEmpty()){
if (objectCount < maxObject){
obj = creat();
objectCount++;
}
}else{
obj = buffer.elementAt(0);
buffer.removeElementAt(0);
}
return obj;
}

public Object get(){
Object obj = _get();

synchronized(this){
while(obj == null){
Thread.yield();
try{wait();}catch(Exception e){}
obj = _get();
}
notifyAll();
}
return obj;
}

public synchronized void free(Object obj){
buffer.addElement(obj);
notifyAll();
}

public synchronized void setMaxSize(int maxSize){
clear();
this.maxObject = maxSize;
buffer.setSize(maxSize);
}

public int getObjectCount(){
return objectCount;
}

public int getActiveObjectCount(){
return objectCount - buffer.size();
}

public synchronized void clear(){
if (buffer.isEmpty())
return;

while(getActiveObjectCount() > 0){
Thread.yield();
try{wait();}catch(Exception e){}
}

Object[] e = elements();
for(int i=0; i close(e);

buffer.removeAllElements();
objectCount = 0;
notifyAll();
}