线程:suspend与resume方法

suspend方法的缺点一: 

   该方法很容易造成公共的同步对象的独占,使得其他线程无法访问公共同步对象。

    

public class Run {
	public static void main(String[] args){
		try{
			final SynchronizedObject2 object = new SynchronizedObject2();
			Thread thread1 = new Thread(){
					@Override
					public void run(){
						object.printString();
					}
			};
			thread1.setName("a");
			thread1.start();
			Thread.sleep(1000);
			Thread thread2 = new Thread(){
				@Override
				public void run(){
					System.out.println("thread2启动了,但进入不了printString()方法! 只打印了1个begin ");
					System.out.println(" 因为printString()方法被a线程锁定并且永远suspend暂停了! ");
					object.printString();
				}
			};
			thread2.start();
		}catch(InterruptedException e){
			e.printStackTrace();
		}
	}
	
	public static void main1(String[] args){
		try {
			MyThread12 thread = new MyThread12();
			thread.start();
			Thread.sleep(5000);
			// A段
			thread.suspend();
			System.out.println("A="+System.currentTimeMillis()+" i="+thread.getI());
			Thread.sleep(5000);
			System.out.println("A="+System.currentTimeMillis()+" i="+thread.getI());
			
			// B段
			thread.resume();
			Thread.sleep(5000);
			
			// C段
			thread.suspend();
			System.out.println("A="+System.currentTimeMillis()+" i="+thread.getI());
			Thread.sleep(5000);
			System.out.println("A="+System.currentTimeMillis()+" i="+thread.getI());
						
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
}





public class SynchronizedObject2 {
	synchronized public void printString(){
		System.out.println("begin");
		if(Thread.currentThread().getName().equals("a")){
			System.out.println("a 线程永远 suspend了 !");
			Thread.currentThread().suspend();
		}
		System.out.println("end");
	}
}

suspend方法的缺点二:

   可能会出现线程的暂停,导致数据不同步

public class Run2 {
	public static void main(String[] args){
		try{
			final MyObject object = new MyObject();
			Thread thread1 = new Thread(){
					@Override
					public void run(){
						object.setValue("a", "aa");
					}
			};
			thread1.setName("a");
			thread1.start();
			Thread.sleep(500);
			Thread thread2 = new Thread(){
				@Override
				public void run(){
					object.printUsernamePassword();
				}
			};
			thread2.start();
		}catch(InterruptedException e){
			e.printStackTrace();
		}
	}
}




public class MyObject {
	private String username = "1";
	private String password = "11";
	
	public void setValue(String u, String p){
		this.username = u;
		if(Thread.currentThread().getName().equals("a")){
			System.out.println("停止a线程");
			Thread.currentThread().suspend();
		}
		this.password = p;
	}
	
	public void printUsernamePassword(){
		System.out.println(username + " " + password);
	}
}