多线程学习--线程优先级-蒲公英云

线程的优先级:继承性，规则性，随机性

线程的优先级具有继承性. 如,线程A启动线程B，则B和A优先级一样
线程的优先级具有规则性. CPU尽量倾向于把资源优先级高的线程
线程的优先级具有随机性. 优先级不等同于执行顺序，二者关系不确定

优先级范围：0~10

继承性：

class MyThread extends Thread {
    @Override
    public void run() {
        System.out.println("MyThread17_1 run priority=" + this.getPriority());
        MyThread2 myThread2 = new MyThread2 ();
        myThread2 .start();
    }
}
class MyThread2 extends Thread {
    @Override
    public void run() {
        System.out.println("MyThread17_2 run priority=" + this.getPriority());
    }
}
public class test{
    public static void main(String[] args) {
        System.out.println("main thread begin priority =" + Thread.currentThread().getPriority());
        //Thread.currentThread().setPriority(6);
        System.out.println("main thread end priority =" + Thread.currentThread().getPriority());
        MyThread myThread = new MyThread ();
        myThread .start();
    }
}

结果：

//Thread.currentThread().setPriority(6);
输出：
main thread begin priority =5
main thread end priority =5
MyThread run priority=5
MyThread2 run priority=5
--------------------
Thread.currentThread().setPriority(6);
输出：
main thread begin priority =5
main thread end priority =6
MyThread run priority=6
MyThread2 run priority=6
规则性：
class MyThread extends Thread {
    @Override
    public void run() {
        long beginTime = System.currentTimeMillis();
        long addResult = 0;
        for (int j = 0; j < 10; j++) {
            for (int i = 0; i < 50000; i++) {
                Random random = new Random();
                random.nextInt();
                addResult += i;
            }
        }
        long endTime = System.currentTimeMillis();
        System.out.println("★★★★★ thread1 use time = " + (endTime - beginTime));
    }
}
class MyThread2 extends Thread {
    @Override
    public void run() {
        long beginTime = System.currentTimeMillis();
        long addResult = 0;
        for (int j = 0; j < 10; j++) {
            for (int i = 0; i < 50000; i++) {
                Random random = new Random();
                random.nextInt();
                addResult += i;
            }
        }
        long endTime = System.currentTimeMillis();
        System.out.println("☆☆☆☆☆ thread2 use time = " + (endTime - beginTime));
    }
}
public class Run18_priority02 {
    public static void main(String[] args) {
        for (int i = 0; i < 5; i++) {
            MyThread myThread = new MyThread ();
            myThread .setPriority(10);
            //myThread .setPriority(1);
            myThread .start();
            MyThread2 myThread2 = new MyThread2 ();
            //myThread2 .setPriority(10);
            myThread2 .setPriority(1);
            myThread2 .start();
        }
    }
}

结果：

myThread.setPriority(10);
myThread2.setPriority(1);
输出：
☆☆☆☆☆ thread2 use time = 202
★★★★★ thread1 use time = 208
★★★★★ thread1 use time = 255
★★★★★ thread1 use time = 261
★★★★★ thread1 use time = 268
★★★★★ thread1 use time = 270
☆☆☆☆☆ thread2 use time = 321
☆☆☆☆☆ thread2 use time = 338
☆☆☆☆☆ thread2 use time = 344
☆☆☆☆☆ thread2 use time = 35
-------------------------
★★★★★ thread1 use time = 121
★★★★★ thread1 use time = 232
☆☆☆☆☆ thread2 use time = 268
☆☆☆☆☆ thread2 use time = 292
★★★★★ thread1 use time = 322
☆☆☆☆☆ thread2 use time = 325
★★★★★ thread1 use time = 387
☆☆☆☆☆ thread2 use time = 390
★★★★★ thread1 use time = 395
☆☆☆☆☆ thread2 use time = 409
----------------------------------------------------
----------------------------------------------------
myThread.setPriority(1);
myThread2.setPriority(10);
输出：
☆☆☆☆☆ thread2 use time = 393
☆☆☆☆☆ thread2 use time = 455
☆☆☆☆☆ thread2 use time = 496
☆☆☆☆☆ thread2 use time = 509
☆☆☆☆☆ thread2 use time = 510
★★★★★ thread1 use time = 511
★★★★★ thread1 use time = 554
★★★★★ thread1 use time = 558
★★★★★ thread1 use time = 561
★★★★★ thread1 use time = 569
---------------
☆☆☆☆☆ thread2 use time = 214
☆☆☆☆☆ thread2 use time = 230
☆☆☆☆☆ thread2 use time = 237
★★★★★ thread1 use time = 257
☆☆☆☆☆ thread2 use time = 261
☆☆☆☆☆ thread2 use time = 271
★★★★★ thread1 use time = 350
★★★★★ thread1 use time = 369
★★★★★ thread1 use time = 339
★★★★★ thread1 use time = 382

随机性：运行顺序。

class MyThread extends Thread {
    @Override
    public void run() {
        long beginTime = System.currentTimeMillis();
        long addResult = 0;
        for (int j = 0; j < 10; j++) {
            for (int i = 0; i < 50000; i++) {
                Random random = new Random();
                random.nextInt();
                addResult += i;
            }
        }
        long endTime = System.currentTimeMillis();
        System.out.println("★★★★★ thread1 use time = " + (endTime - beginTime));
    }
}
class MyThread2 extends Thread {
    @Override
    public void run() {
        long beginTime = System.currentTimeMillis();
        long addResult = 0;
        for (int j = 0; j < 10; j++) {
            for (int i = 0; i < 50000; i++) {
                Random random = new Random();
                random.nextInt();
                addResult += i;
            }
        }
        long endTime = System.currentTimeMillis();
        System.out.println("☆☆☆☆☆ thread2 use time = " + (endTime - beginTime));
    }
}
public class Run18_priority02 {
    public static void main(String[] args) {
        for (int i = 0; i < 5; i++) {
            MyThread myThread = new MyThread ();
            myThread .setPriority(5);
            myThread .start();
            MyThread2 myThread2 = new MyThread2 ();
            myThread2 .setPriority(6);
            myThread2 .start();
        }
    }
}

结果：

☆☆☆☆☆ thread2 use time = 981
★★★★★ thread1 use time = 992
★★★★★ thread1 use time = 996
☆☆☆☆☆ thread2 use time = 1034
☆☆☆☆☆ thread2 use time = 1137
☆☆☆☆☆ thread2 use time = 1138
☆☆☆☆☆ thread2 use time = 1150
★★★★★ thread1 use time = 1182
★★★★★ thread1 use time = 1185
★★★★★ thread1 use time = 1188