public class ConnThreadLocal {

	public static ThreadLocal<String> th = new ThreadLocal<String>();
	
	public void setTh(String value){
		th.set(value);
	}
	public void getTh(){
		System.out.println(Thread.currentThread().getName() + ":" + this.th.get());
	}
	
	public static void main(String[] args) throws InterruptedException {
		
		final ConnThreadLocal ct = new ConnThreadLocal();
		Thread t1 = new Thread(new Runnable() {
			@Override
			public void run() {
				ct.setTh("張三");
				ct.getTh();
			}
		}, "t1");
		
		Thread t2 = new Thread(new Runnable() {
			@Override
			public void run() {
				try {
					Thread.sleep(1000);
					ct.getTh();
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
			}
		}, "t2");
		
		t1.start();
		t2.start();
	}
	
}
 

public class Singletion {
	
	private static class InnerSingletion {
		private static Singletion single = new Singletion();
	}
	
	public static Singletion getInstance(){
		return InnerSingletion.single;
	}
	
}

public class DubbleSingleton {

	private static DubbleSingleton ds;
	
	public  static DubbleSingleton getDs(){
		if(ds == null){
			try {
				//模擬初始化物件的準備時間...
				Thread.sleep(3000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			synchronized (DubbleSingleton.class) {
				if(ds == null){
					ds = new DubbleSingleton();
				}
			}
		}
		return ds;
	}
	
	public static void main(String[] args) {
		Thread t1 = new Thread(new Runnable() {
			@Override
			public void run() {
				System.out.println(DubbleSingleton.getDs().hashCode());
			}
		},"t1");
		Thread t2 = new Thread(new Runnable() {
			@Override
			public void run() {
				System.out.println(DubbleSingleton.getDs().hashCode());
			}
		},"t2");
		Thread t3 = new Thread(new Runnable() {
			@Override
			public void run() {
				System.out.println(DubbleSingleton.getDs().hashCode());
			}
		},"t3");
		
		t1.start();
		t2.start();
		t3.start();
	}
	
}