Android-Java-Thread的使用

main线程跑三个任务：

package android.java.thread2;

class Demo {

    private String name;

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

    public void showMethod() {
        for (int i = 0; i < 10; i++) {
            System.out.println("Demo showMethod >>>>>>>" + name + " " + i);
        }
    }
}

public class Test {

    public static void main(String[] args) {

        Demo demo1 = new Demo("步惊云");
        
        Demo demo2 = new Demo("秦霜");

        // 任务1 >>>main线程在执行
        demo1.showMethod();
        
        // 任务2 >>>main线程在执行
        demo2.showMethod();

        // 任务3 >>>main线程在执行
        for (int i = 0; i < 10; i++) {
            System.out.println("Test main " + i);
        }
    }

}

执行的结果：

Demo showMethod >>>>>>>步惊云 0
Demo showMethod >>>>>>>步惊云 1
Demo showMethod >>>>>>>步惊云 2
Demo showMethod >>>>>>>步惊云 3
Demo showMethod >>>>>>>步惊云 4
Demo showMethod >>>>>>>步惊云 5
Demo showMethod >>>>>>>步惊云 6
Demo showMethod >>>>>>>步惊云 7
Demo showMethod >>>>>>>步惊云 8
Demo showMethod >>>>>>>步惊云 9
Demo showMethod >>>>>>>秦霜 0
Demo showMethod >>>>>>>秦霜 1
Demo showMethod >>>>>>>秦霜 2
Demo showMethod >>>>>>>秦霜 3
Demo showMethod >>>>>>>秦霜 4
Demo showMethod >>>>>>>秦霜 5
Demo showMethod >>>>>>>秦霜 6
Demo showMethod >>>>>>>秦霜 7
Demo showMethod >>>>>>>秦霜 8
Demo showMethod >>>>>>>秦霜 9
Test main 0
Test main 1
Test main 2
Test main 3
Test main 4
Test main 5
Test main 6
Test main 7
Test main 8
Test main 9

从以上结果可以看出：

　　这三个任务都是被main这一个线程来完成的，这样会造成 demo1.showMethod(); 执行的时候 demo2.showMethod(); 任务3处于等待状态

---

三个任务同时执行，使用Thread

package android.java.thread2;

class Demo extends Thread { // 继承Thread 并重写 run() 方法，属于定义一个线程子类

    private String name;

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

    /**
     * run方法里面执行的是start线程里面执行任务
     */
    @Override
    public void run() {
        super.run();
        showMethod();
    }

    public void showMethod() {
        for (int i = 0; i < 10; i++) {
            System.out.println("Demo showMethod >>>>>>>" + name + " " + i);
        }
    }
}

public class Test {

    public static void main(String[] args) {

        Demo demo1 = new Demo("步惊云");

        Demo demo2 = new Demo("秦霜");

        // 任务1 >>>启动一个新线程去执行任务
        demo1.start();

        // 任务2 >>>启动一个新线程去执行任务
        demo2.start();

        // 任务3 >>>main线程在执行
        for (int i = 0; i < 10; i++) {
            System.out.println("Test main " + i);
        }
    }

}

第一次执行结果：

Demo showMethod >>>>>>>步惊云 0
Demo showMethod >>>>>>>秦霜 0
Demo showMethod >>>>>>>秦霜 1
Demo showMethod >>>>>>>秦霜 2
Demo showMethod >>>>>>>秦霜 3
Demo showMethod >>>>>>>步惊云 1
Demo showMethod >>>>>>>步惊云 2
Demo showMethod >>>>>>>步惊云 3
Demo showMethod >>>>>>>步惊云 4
Demo showMethod >>>>>>>步惊云 5
Demo showMethod >>>>>>>步惊云 6
Demo showMethod >>>>>>>步惊云 7
Demo showMethod >>>>>>>秦霜 4
Demo showMethod >>>>>>>秦霜 5
Demo showMethod >>>>>>>秦霜 6
Demo showMethod >>>>>>>秦霜 7
Demo showMethod >>>>>>>秦霜 8
Demo showMethod >>>>>>>秦霜 9
Test main 0
Test main 1
Demo showMethod >>>>>>>步惊云 8
Demo showMethod >>>>>>>步惊云 9
Test main 2
Test main 3
Test main 4
Test main 5
Test main 6
Test main 7
Test main 8
Test main 9

第二次执行结果：

Demo showMethod >>>>>>>步惊云 0
Demo showMethod >>>>>>>步惊云 1
Demo showMethod >>>>>>>步惊云 2
Demo showMethod >>>>>>>步惊云 3
Demo showMethod >>>>>>>步惊云 4
Demo showMethod >>>>>>>步惊云 5
Demo showMethod >>>>>>>步惊云 6
Demo showMethod >>>>>>>步惊云 7
Demo showMethod >>>>>>>步惊云 8
Demo showMethod >>>>>>>步惊云 9
Demo showMethod >>>>>>>秦霜 0
Demo showMethod >>>>>>>秦霜 1
Demo showMethod >>>>>>>秦霜 2
Test main 0
Test main 1
Test main 2
Test main 3
Test main 4
Test main 5
Test main 6
Test main 7
Test main 8
Test main 9
Demo showMethod >>>>>>>秦霜 3
Demo showMethod >>>>>>>秦霜 4
Demo showMethod >>>>>>>秦霜 5
Demo showMethod >>>>>>>秦霜 6
Demo showMethod >>>>>>>秦霜 7
Demo showMethod >>>>>>>秦霜 8
Demo showMethod >>>>>>>秦霜 9

第三次执行结果：

Demo showMethod >>>>>>>步惊云 0
Demo showMethod >>>>>>>秦霜 0
Demo showMethod >>>>>>>秦霜 1
Demo showMethod >>>>>>>秦霜 2
Demo showMethod >>>>>>>秦霜 3
Demo showMethod >>>>>>>秦霜 4
Test main 0
Test main 1
Test main 2
Test main 3
Test main 4
Test main 5
Test main 6
Test main 7
Test main 8
Test main 9
Demo showMethod >>>>>>>秦霜 5
Demo showMethod >>>>>>>秦霜 6
Demo showMethod >>>>>>>秦霜 7
Demo showMethod >>>>>>>秦霜 8
Demo showMethod >>>>>>>秦霜 9
Demo showMethod >>>>>>>步惊云 1
Demo showMethod >>>>>>>步惊云 2
Demo showMethod >>>>>>>步惊云 3
Demo showMethod >>>>>>>步惊云 4
Demo showMethod >>>>>>>步惊云 5
Demo showMethod >>>>>>>步惊云 6
Demo showMethod >>>>>>>步惊云 7
Demo showMethod >>>>>>>步惊云 8
Demo showMethod >>>>>>>步惊云 9

以上三次结果是由CPU非常快速切换决定的