【Java】Java多线程的简单使用

import java.util.*;
public class ThreadsTest extends Thread{
    private String name;
    private int time;
    public ThreadsTest(int time,String name){
        this.time = time;
        this.name = name;
    }
    public void run() {
        while (true) {
            try {
                System.out.println(name+":"+Calendar.getInstance().getTime());
                Thread.sleep(time);
            }catch(InterruptedException e) {}
        }
    }
    public static void main(String[] args) {
        ThreadsTest fast = new ThreadsTest(1000,"Fast");
        ThreadsTest slow = new ThreadsTest(3000,"Slow");
        fast.start();
        slow.start();
    }
}

效果如图：

有临界资源，用synchronized修饰代码块或方法，可实现某一时刻只有一个线程拥有对象锁

以堆栈举例：

public class Stack{
    int idx = 0;
    char[] data = new char[10];
    public void push(char c) {
        synchronized (this) { //方法一，用在代码块
            data[idx] = c;
            idx++;
        }
    }
    public synchronized char pop() { //方法二，用在描述对象
        idx--;
        return data[idx];
    }
}

wait()方法和notify()方法，wait()方法使线程进入阻塞状态，释放占用的对象锁。notify()方法和notifyAll()方法，前者随机唤醒等待中的一个线程，后者使等待队列中的全部线程解除阻塞。

实现Runnable接口

class TimePrinter implements Runnable{
    //此处省略代码,只有构造对象时候不同
    public static void main(String[] args) {
        Thread fast = new Thread(new TimePrinter(1000,"Fast"));
        Thread slow = new Thread(new TimePrinter(1000,"slow"));
        fast.start();
        slow.start();
    }
}