多线程学习--线程优先级

你的名字 2023-10-27 06:29 165阅读 0赞

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