ReentrantLock 是JDK中內建鎖，也稱可重入鎖，API也較為簡單。

 Condition 可實現 執行緒間通訊，由ReentrantLock 例項產生即 lock.new Condition();

下面這個demo模擬最簡單的生產者 消費者模式，Add執行緒模擬生產者執行生產任務，Get任務執行模擬消費者執行消費任務，Task類種有add和get兩個方法一個用於生產物件，一個用於消費物件。

package test.concurrent;

import java.util.ArrayList;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class TestCondition {
	public static ArrayList list = new ArrayList();
	
	public static void main(String[] args) {
		ExecutorService threadPool = Executors.newFixedThreadPool(2);
		threadPool.execute(new Add());
		threadPool.execute(new Get());
	}
	
	public static class Task{
		private static Lock lock= new ReentrantLock();
		
		private static Condition condition = lock.newCondition();
		
		public static void add(Object obj) {
			lock.lock();
			try {
				list.add(obj);
				System.out.println("有新成員加入"+obj);
				condition.signal();
			} catch (Exception e) {
				// TODO: handle exception
			}finally {
				lock.unlock();
			}
		}
		
		public static void get() {
			lock.lock();
			try {
				while(list.size()<0) {
					condition.await();
				}
				System.out.println("取出；"+list.remove(0));
			} catch (Exception e) {
				// TODO: handle exception
			}finally {
				lock.unlock();
			}
		}
	}
	
	/**
	 * 存錢
	 * @author Administrator
	 *
	 */
	public static class Add implements Runnable{

		@Override
		public void run() {
			// TODO Auto-generated method stub
			while(true) {
				Task.get();
			}
		}
	}
	/**
	 * 取錢
	 * @author Administrator
	 *
	 */
	public static class Get implements Runnable{
		@Override
		public void run() {
			// TODO Auto-generated method stub
			int i =0;
			while(true) {
				i++;
				Task.add("我是第："+i+"個");
				try {
					Thread.sleep(2000);
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}
	}
	
}