多线程基础

java中启动多线程有两种方法，一是继承Thread类，二是实现Runnable接口。

继承Thread类：

java中正确地启动多线程不能直接调用run（）方法，而是调用从Thread类中继承而来的start（）方法。

class myThead01 extends Thread {
    private String name;

    public myThead01(String n) {
        this.name = n;
    }

    @Override
    public void run() {
        for (int i = 0; i < 100; i++) {
            System.out.println(name+" :"+i);
        }
    }
}

public class ThreadDemo01 {
    public static void main(String[] args) {
        myThead01 mt1 = new myThead01("A");
        myThead01 mt2 = new myThead01("B");
        mt1.start();
        mt2.start();
    }

}

实现Runnable接口：

在Thread类中提供了public Thread(Runnable target)和public Thread(Runnable target,String name)两个构造方法，

这两个构造方法都可以接受Runnable的子类实例对象，所以可以依靠此点启动多线程：

class MyThread02 implements Runnable {
    private String name;

    public MyThread02(String name) {
        this.name = name;
    }

    @Override
    public void run() {
        for (int i = 0; i < 10; i++) {
            System.out.println(name + "runing,i= " + i);
        }

    }

}

public class RunnableDemo01 {
    public static void main(String[] args) {
        MyThread02 my1 = new MyThread02("AAAA");
        MyThread02 my2 = new MyThread02("BBBB");
        Thread t1 = new Thread(my1);
        Thread t2 = new Thread(my2);
        t1.start();
        t2.start();
    }
}

优缺点比较：

继承Thread不能保证资源共享：

class myThread04 extends Thread{
    private String nameString;
    private int tiket=5;
    public myThread04(String name){
        nameString=name;
    }
    public void run() {
        for(int i=1;i<100;i++){
            if(tiket>0){
            System.out.println(nameString+":"+tiket--);
            }
        }
    }
}
public class ThreadDemo04 {
    public static void main(String[] args) {
         myThread04 mThread01=new myThread04("aaaaaa");
         myThread04 mThread02=new myThread04("bbbbbb");
         myThread04 mThread03=new myThread04("cccccc");
        
         mThread01.start();   
         mThread02.start();
         mThread03.start();
    }
}

实现runnable可以：

class myThread05 implements Runnable {

    private int tiket = 5;
    private String nameString;

    public myThread05(String name) {
        nameString = name;
    }

    public void run() {
        for (int i = 0; i < 100; i++) {
            if (tiket > 0) {
                System.out.println(nameString + ":" + tiket--);
            }
        }
    }

}

public class RunnableDemo05 {
    public static void main(String[] args) {
        myThread05 m = new myThread05("aa");

        Thread thread = new Thread(m);
        thread.start();
    }

}