线程优先级

Java提供一个线程调度器来监控程序中启动后进入就绪状态的所有线程。线程调 度器按照线程的优先级决定应调度哪个线程来执行。
线程的优先级用数字表示，范围从1到10

• Thread.MIN_PRIORITY = 1
• Thread.MAX_PRIORITY = 10
• Thread.NORM_PRIORITY = 5

使用下述方法获得或设置线程对象的优先级。

• int getPriority();
• void setPriority(int newPriority);

优先级的设定建议在start()调用前

注意：优先级低只是意味着获得调度的概率低。并不是绝对先调用优先级高后调 用优先级低的线程。

 代码示例：

package com.sxt.state;

/**
 * 线程的优先级1-10
 * MAX_PRIORITY 5默认
 * MIN_PRIORITY 1
 * NORM_PRIORITY 10
 * 优先级不代表绝对的先后顺序，代表概率
 */
public class PriorityTest {

    public static void main(String[] args) {
        System.out.println(Thread.currentThread().getPriority());

        MyPriority mp = new MyPriority();
        Thread t1 = new Thread(mp,"adidas");
        Thread t2 = new Thread(mp,"NIKE");
        Thread t3 = new Thread(mp,"回力");
        Thread t4 = new Thread(mp,"乔丹");
        Thread t5 = new Thread(mp,"李宁");
        Thread t6 = new Thread(mp,"双星");

        //在启动前这只优先级
        t1.setPriority(Thread.MAX_PRIORITY);
        t2.setPriority(Thread.MAX_PRIORITY);
        t3.setPriority(Thread.MAX_PRIORITY);
        t4.setPriority(Thread.MIN_PRIORITY);
        t5.setPriority(Thread.MIN_PRIORITY);
        t6.setPriority(Thread.MIN_PRIORITY);
        t1.start();
        t2.start();
        t3.start();
        t4.start();
        t5.start();
        t6.start();

    }
}

class MyPriority implements Runnable{

    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName()+"-->"+Thread.currentThread().getPriority());

    }
}

代码示例：

package com.sxt.state;

/**
 * 守护线程：是为用户线程服务的；jvm停止不用等待守护线程执行完毕
 * 默认：用户线程 jvm等待用户线程执行完毕才会停止
 *
 */
public class DaemonTest {

    public static void main(String[] args) {
        God god = new God();
        You you = new You();
        Thread t = new Thread(god);
        t.setDaemon(true);//将用户线程调整为守护
        t.start();
        new Thread(you).start();
    }
}

class You implements Runnable{
    @Override
    public void run() {
        for (int i = 1; i <= 365*100; i++) {
            System.out.println("happy life...");
        }

        System.out.println("oooooo...");
    }
}

class God implements Runnable{

    @Override
    public void run() {
        for (;true;) {
            System.out.println("bless you...");
        }
    }
}

daemon：守护进程，后台程序

• 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、监控内存使用等。

常用其他方法

代码示例：

package com.sxt.state;

/**
 * 其他方法
 * isAlive：线程是否还活着
 * Thread.currentThread()：当前线程
 * setName、getName：代理名称
 */
public class InfoTest {

    public static void main(String[] args) throws InterruptedException {
        System.out.println(Thread.currentThread().isAlive());
        //设置名称：真实角色+代理角色
        MyInfo info = new MyInfo("战斗机");
        Thread t = new Thread(info);
        t.setName("公鸡");
        t.start();
        Thread.sleep(1000);
        System.out.println(t.isAlive());

    }
}

class MyInfo implements Runnable{

    private String name;

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

    @Override
    public void run() {
        System.out.println(Thread.currentThread().getName()+"-->"+name);
    }
}