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https://www.cnblogs.com/dolphin0520/p/3920407.html

public class UnsafeTask implements Runnable {	private Date startDate;	@Override	public void run() {		startDate = new Date();		System.out.printf("Starting Thread: %s : %s\n", Thread.currentThread().getId(), startDate);		try {			TimeUnit.SECONDS.sleep((int) Math.rint(Math.random() * 10));		} catch (InterruptedException e) {			e.printStackTrace();		}		System.out.printf("Thread Finished: %s : %s\n", Thread.currentThread().getId(), startDate);	}}

第一种，同一个Runnable对象时

public class Core {	public static void main(String[] args) {		UnsafeTask task=new UnsafeTask(); 		 for (int i=0; i<10; i++){//		UnsafeTask task=new UnsafeTask();		Thread thread=new Thread(task);		thread.start();		try { TimeUnit.SECONDS.sleep(2);		} catch (InterruptedException e) {		e.printStackTrace();		}		}	}}

你会发现Thread Finished:的时间是相同的。

public static void main(String[] args) {//		UnsafeTask task=new UnsafeTask(); 		 for (int i=0; i<10; i++){		UnsafeTask task=new UnsafeTask();		Thread thread=new Thread(task);		thread.start();		try { TimeUnit.SECONDS.sleep(2);		} catch (InterruptedException e) {		e.printStackTrace();		}		}	}

使用Threadlocal的方式

public class UnsafeTask implements Runnable {	// private Date startDate;	private static ThreadLocal
   
     startDate = new ThreadLocal
    
     () {		protected Date initialValue() {			return new Date();		}	};	@Override	public void run() {		System.out.printf("Starting Thread: %s : %s\n", Thread.currentThread().getId(), startDate.get());		try {			TimeUnit.SECONDS.sleep((int) Math.rint(Math.random() * 10));		} catch (InterruptedException e) {			e.printStackTrace();		}		System.out.printf("Thread Finished: %s : %s\n", Thread.currentThread().getId(), startDate.get());	}}
    
   

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