java 線程安全的隊列模擬

import java.util.LinkedList;  
import java.util.concurrent.locks.Condition;  
import java.util.concurrent.locks.Lock;  
import java.util.concurrent.locks.ReentrantLock;  

public class CustomerQueue {  

    private static final int SIZE = 5000;  
    private LinkedList<String> queue = new LinkedList<String>();  
    private Lock lock = new ReentrantLock();  
    private Condition full = lock.newCondition();  
    private Condition empty = lock.newCondition();  

    private static CustomerQueue manager = new CustomerQueue();  

    private CustomerQueue(){  

    }  

    public static CustomerQueue getQueue(){  

        return manager;  
    }  

    public void put(String phone){  

        lock.lock();  

        try {  
            while (queue.size() == SIZE) {  
                full.await();  
            }  
            queue.addFirst(phone);    
            empty.signal();  
        } catch (InterruptedException e) {  
            e.printStackTrace();  
        } finally{  
            lock.unlock();  
        }  
    }  

    public LinkedList<String> takeAll(){  

        LinkedList<String> retVal = new LinkedList<String>();  

        lock.lock();  

        try {  
            while (queue.size() == 0) {  
                empty.await();  
            }  

            retVal.addAll(queue);  
            queue.clear();            
            full.signal();  
        } catch (InterruptedException e) {  
            e.printStackTrace();  
        } finally{  
            lock.unlock();  
        }  
        return retVal;  
    }  
}