函数式接口lambda

函数式接口 Lambda表达式

• 函数式接口定义

  • 任何接口，如果只包含唯一一个抽象方法，那么它就是函数式接口

  • public interface Runnable{
        public abstract void run();
    }
    

• 对于函数式接口，可以通过 Lambda 表达式来创建该接口的对象

  • package com.fjbc.test;
    
    import java.util.ArrayList;
    import java.util.List;
    
    public class Test {
        public static void main(String[] args) {
            ILike like = null;
            like = () -> {
                System.out.println("i like lambda5");
            };
            like.like();
        }
    }
    //1.定义一个函数式接口
    interface ILike{
        void like();
    }
    

线程状态

线程休眠_sleep

package com.fjbc.test;

public class Test倒计时{
    public static void main(String[] args){
        try {
            tenDown();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    public static void tenDown() throws InterruptedException {
            int num = 10;
            while(true){
                Thread.sleep(1000);
                System.out.println(num--);
                if(num <= 0){
                    break;
                }
            }
        }
}

线程礼让—yield(让CPU重新调用，礼让不一定成功！看CPU心情)

线程强制执行—join

观测线程状态

package com.fjbc.多线程;

/**
 * 观察测试线程状态
 */
public class Demo21_ThreadState {
    public static void main(String[] args) throws InterruptedException {
        Thread thread = new Thread(() -> {
            for (int i = 0; i < 5; i++) {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            System.out.println("//");
        });
        //观察状态
        Thread.State state = thread.getState();
        System.out.println(state);
        //观察启动后
        thread.start();
        state = thread.getState();
        System.out.println(state);//Run
        while (state != Thread.State.TERMINATED) {//只要现成不终止,就一直输出状态
            Thread.sleep(100);
            state = thread.getState();//更新线程状态
            System.out.println(state);
        }
        //死亡后的线程不能再启动了,启动会报异常
        //thread.start();
    }
}

线程的优先级

• 优先级低只是意味着获得调度的概率低，并不是优先级低就不会被调用了，还是得看CPU心情

/**
 * 线程优先级
 */
public class Demo22_ThreadPriority{
    public static void main(String[] args) {
        //主线程默认优先级
        System.out.println(Thread.currentThread().getName()+"-->"+Thread.currentThread().getPriority());

        MyPriority myPriority = new MyPriority();
        Thread thread1 = new Thread(myPriority);
        Thread thread2 = new Thread(myPriority);
        Thread thread3 = new Thread(myPriority);
        Thread thread4 = new Thread(myPriority);
        Thread thread5 = new Thread(myPriority);

        //先设置优先级,再启动
        thread1.start();

        thread2.setPriority(1);
        thread2.start();

        thread3.setPriority(4);
        thread3.start();

        thread4.setPriority(Thread.MAX_PRIORITY);//MAX_PRIORITY=10
        thread4.start();

        thread5.setPriority(8);
        thread5.start();
    }
}
class MyPriority implements Runnable{
    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName()+"-->"+Thread.currentThread().getPriority());
    }
}

守护线程（daemon）

• 线程分为用户线程和守护线程

• 虚拟机必须确保用户线程执行完毕

• 虚拟机不用等待守护线程执行完毕

• 如，后台记录操作日志，监控内存，垃圾回收等待

  • package com.fjbc.多线程;
    
    /**
     * 测试守护线程
     * 上帝守护你
     */
    public class Demo23_DaemonThread {
        public static void main(String[] args) {
            God god = new God();
            You you = new You();
    
            Thread thread = new Thread(god);
            //默认false表示是用户线程,正常的线程都是用户线程...
            thread.setDaemon(true);
            //上帝守护线程启动
            thread.start();
            //你 用户线程启动
            new Thread(you).start();
        }
    }
    
    //上帝
    class God implements Runnable{
        @Override
        public void run() {
            while (true){
                System.out.println("上帝保佑着你");
            }
        }
    }
    
    //你
    class You implements Runnable{
        @Override
        public void run() {
            for (int i = 0; i < 36500; i++) {
                System.out.println("你一生都开心的活着");
            }
            System.out.println("====goodbye!world====");
        }
    }