多线程的实现三种方式

Posted 2021-02-14 xiufengchen

多线程的实现三种方式:
1 继承thread类,重写run方法
继承thread方法就可以i调用thread类的start方法,,start方法调用java natvie start0();
这个是调用操作系统的方法,start方法

package com.cxy;



class Mythread01 extends  Thread{
    @Override
    public void run(){
        System.out.println("iii");
    }}
public class Mythread {
    public static void main(String[] args) {
        Mythread01 my = new Mythread01();
        my.start();
    }


}

2 实现runnable接口
接口实现是没有start方法,但是多线程必须采用start方法,所以需要调用new thread(mythread)
再调用start方法.

package com.cxy;


import sun.security.krb5.internal.Ticket;

class MyThread implements  Runnable{
    private Integer ticket=10;
    @Override
    public void  run() {
        synchronized (this) {
            for (int i = 0; i < 10; i++) {
                System.out.println("zhgee" + i);
                System.out.println(ticket);
                ticket--;
                if (ticket<0){
                    break;
                }
            }
        }
    }
}
public class RunnableDemo {
    public static void main(String[] args) {
        MyThread myThread=new MyThread();
        new Thread(myThread).start();
        new Thread(myThread).start();
    }
}

前两中方法的区别:
thread类是runnable的接口子类,可以有效避免单继承的局限性
runnable接口可以很好的体现数据共享概念
如果继承thread类,那么就可以继承sart方法,runnable接口中,需要构建thread对象调用thread的start方法

3 实现callable接口

 

package com.cxy;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;

class CallableThread implements Callable<String> {
    private Integer ticket = 10;

    @Override
    public String call() throws Exception {
        synchronized (this) {
            for (int i = 0; i < 10; i++) {
                System.out.println("zhgee" + i);
                System.out.println(ticket);
                ticket--;
                if (ticket < 0) {
                    break;
                }
            }
            return "票卖完了";
        }

    }
}
public class CallableDemo {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        CallableThread callableThread=new CallableThread();
        CallableThread callableThread1=new CallableThread();
        FutureTask<String> futureTask=new FutureTask(callableThread);
        FutureTask<String> futureTask1=new FutureTask(callableThread1);
        new Thread(futureTask).start();
        new Thread(futureTask1).start();
        System.out.println(futureTask.get());
        System.out.println(futureTask1.get());

    }

}

三个方法都必须调用start方法才可以启动线程

    public synchronized void start() {
        /**
         * This method is not invoked for the main method thread or "system"
         * group threads created/set up by the VM. Any new functionality added
         * to this method in the future may have to also be added to the VM.
         *
         * A zero status value corresponds to state "NEW".
         */
        if (threadStatus != 0)
            throw new IllegalThreadStateException();

        /* Notify the group that this thread is about to be started
         * so that it can be added to the group‘s list of threads
         * and the group‘s unstarted count can be decremented. */
        group.add(this);

        boolean started = false;
        try {
            start0();
            started = true;
        } finally {
            try {
                if (!started) {
                    group.threadStartFailed(this);
                }
            } catch (Throwable ignore) {
                /* do nothing. If start0 threw a Throwable then
                  it will be passed up the call stack */
            }
        }
    }

    private native void start0();

private native void start0();这个方法是用native修饰,表示调用操作系统的本地方法,所以就需要调用操作系统的方法