千锋逆战班，Day29

在千锋逆战学习Java的第29天

今天学习了多线程的同步规则、等待（wait）与通知（notify）、线程池的概念和原理、Callable接口和Future接口。

作业题：
8.有以下代码

public class TestMyThread {
	public static void main(String[] args) {
		Thread t1 = new MyThread("aaa");
		Thread t2 = new MyThread("bbb");
		t1.start();
		t2.start();
	}
}

class MyThread extends Thread {
	private String data;

	public MyThread(String data) {
		this.data = data;
	}

	public void run() {
		for (int i = 0; i < 100; i++) {
			System.out.println(data);
		}
	}
}

答：C，out是System类里的一个属性，对out这个属性加锁，t1、t2用的System.out是同一个

9.代码改错

public class TestMyThread {
	public static void main(String[] args) {
		Runnable t1 = new MyThread1();
		Thread t2 = new MyThread2();
		t1.start();
		t2.start();
	}
}

class MyThread1 implements Runnable{
	public void run(){
		for(int i =0; i<100;i++){
			this.sleep((int)(Math.random()*1000));
			System.out.println("hello");
		}
	}
}
class MyThread2 extends Thread{
	public void run() throws Exception{
		for(int i= 0; i<100; i++){
			this.sleep((int)(Math.random()*1000));
			System.out.println("world");
		}
	}
}

修改后代码如下：

public class TestMyThread {
	public static void main(String[] args) {
		Runnable t1 = new MyThread1();
		Thread t2 = new MyThread2();
		// 错误。t1不是线程，是一个任务类对象，要传入一个线程对象
		Thread t3 = new Thread(t1);
		t3.start();
		t2.start();
	}
}

class MyThread1 implements Runnable {
	public void run() {
		for (int i = 0; i < 100; i++) {
			//错误。MyThread1没有sleep方法，要用Thread直接调用sleep方法，并用tryCatch处理异常
			try {
				Thread.sleep((int) (Math.random() * 1000));
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			System.out.println("hello");
		}
	}
}

class MyThread2 extends Thread {
	// 错误。run方法不能声明异常
	public void run() {
		for (int i = 0; i < 100; i++) {
			// 错误。用tryCatch语句处理this.sleep()异常
			try {
				this.sleep((int) (Math.random() * 1000));
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			System.out.println("world");
		}
	}
}