Java多线程（一）

一、创建线程

     第一种方式：继承Thread

步骤：

1，定义类继承Thread

2，复写Thread类中的 run 方法，目的是将自定义的代码存储在run方法，让线程运行

3，调用线程的start方法，该方法有两个作用：启动线程，调用run方法；

public class ThreadDemo {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Demo demo = new Demo();
  		demo.start();
		for (int i = 0; i < 30; i++) {
			System.out.println("main ==== "+i);
		}
	}
}

class Demo extends Thread{
	public void run() {
	for (int i = 0; i < 30; i++) {
		System.out.println("demo run---- "+i);
		}		
	}
}

运行结果如下：

main ==== 0
main ==== 1
main ==== 2
main ==== 3
main ==== 4
main ==== 5
main ==== 6
demo run---- 0
demo run---- 1
demo run---- 2
demo run---- 3
demo run---- 4
main ==== 7
main ==== 8
main ==== 9
main ==== 10
main ==== 11
main ==== 12
main ==== 13
main ==== 14
main ==== 15
main ==== 16
main ==== 17
main ==== 18
demo run---- 5
main ==== 19
main ==== 20
main ==== 21
main ==== 22
main ==== 23
main ==== 24
demo run---- 6
main ==== 25
main ==== 26
main ==== 27
main ==== 28
main ==== 29
demo run---- 7
demo run---- 8
demo run---- 9
demo run---- 10
demo run---- 11
demo run---- 12
demo run---- 13
demo run---- 14
demo run---- 15
demo run---- 16
demo run---- 17
demo run---- 18
demo run---- 19
demo run---- 20
demo run---- 21
demo run---- 22
demo run---- 23
demo run---- 24
demo run---- 25
demo run---- 26
demo run---- 27
demo run---- 28
demo run---- 29

可以看到主线程和demo线程交替运行。

如果将demo.start() 替换成demo.run，则此程序变为单线程程序，即没有启动线程，而是按顺序依次去执行方法，如：

public class ThreadDemo {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Demo demo = new Demo();
//		demo.start();
      //仅仅只是对象调用方法。尽管线程创建了，但是未被启动运行
		demo.run();
		for (int i = 0; i < 30; i++) {
			System.out.println("main ==== "+i);
		}
	}
}

class Demo extends Thread{
	public void run() {
	for (int i = 0; i < 30; i++) {
		System.out.println("demo run---- "+i);
		}	
	}
}

执行结果：

demo run---- 0
demo run---- 1
demo run---- 2
demo run---- 3
demo run---- 4
demo run---- 5
demo run---- 6
demo run---- 7
demo run---- 8
demo run---- 9
demo run---- 10
demo run---- 11
demo run---- 12
demo run---- 13
demo run---- 14
demo run---- 15
demo run---- 16
demo run---- 17
demo run---- 18
demo run---- 19
demo run---- 20
demo run---- 21
demo run---- 22
demo run---- 23
demo run---- 24
demo run---- 25
demo run---- 26
demo run---- 27
demo run---- 28
demo run---- 29
main ==== 0
main ==== 1
main ==== 2
main ==== 3
main ==== 4
main ==== 5
main ==== 6
main ==== 7
main ==== 8
main ==== 9
main ==== 10
main ==== 11
main ==== 12
main ==== 13
main ==== 14
main ==== 15
main ==== 16
main ==== 17
main ==== 18
main ==== 19
main ==== 20
main ==== 21
main ==== 22
main ==== 23
main ==== 24
main ==== 25
main ==== 26
main ==== 27
main ==== 28
main ==== 29

二、线程的几种状态：

被创建、运行、冻结、阻塞、消亡。

“阻塞” 指：具备运行资格，但没有执行权。那些处于交替获取执行权中，但还没获得执行权的线程的状态；

“冻结”指：放弃执行资格，等待被唤醒或者休眠时间还未结束的线程所处于的状态；

这五种状态的关系如图所示：

三、线程名称

线程都有自己默认的名称。格式：“Thread-编号” ，该编号从0开始。可以调用Thread的 setName() 和getName()方法

public class ThreadDemo {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Demo d1 = new Demo();
		Demo d2 = new Demo();
		d1.start();
		d2.start();

		for (int i = 0; i < 30; i++) {
			System.out.println("main ==== "+i);
		}
	}
}

class Demo extends Thread{
	public void run() {
	for (int i = 0; i < 30; i++) {
		System.out.println(this.getName()+" run---- "+i);
		}	
	}
}

运行结果：

main ==== 0
main ==== 1
main ==== 2
main ==== 3
Thread-1 run---- 0
Thread-0 run---- 0
Thread-1 run---- 1
Thread-1 run---- 2
Thread-1 run---- 3
Thread-1 run---- 4
Thread-1 run---- 5
Thread-1 run---- 6
Thread-1 run---- 7
Thread-1 run---- 8
Thread-1 run---- 9
main ==== 4
main ==== 5
main ==== 6
main ==== 7
main ==== 8
main ==== 9
main ==== 10
Thread-1 run---- 10
Thread-0 run---- 1
Thread-0 run---- 2
Thread-0 run---- 3
Thread-0 run---- 4
Thread-0 run---- 5
Thread-0 run---- 6
Thread-0 run---- 7
Thread-1 run---- 11
main ==== 11
main ==== 12
main ==== 13
Thread-1 run---- 12
Thread-1 run---- 13
Thread-0 run---- 8
Thread-0 run---- 9
Thread-0 run---- 10
Thread-0 run---- 11
Thread-0 run---- 12
Thread-0 run---- 13
Thread-0 run---- 14
Thread-0 run---- 15
Thread-0 run---- 16
Thread-0 run---- 17
Thread-0 run---- 18
Thread-0 run---- 19
Thread-1 run---- 14
main ==== 14
main ==== 15
main ==== 16
main ==== 17
main ==== 18
main ==== 19
Thread-1 run---- 15
Thread-1 run---- 16
Thread-1 run---- 17
Thread-1 run---- 18
Thread-1 run---- 19

给线程设定名称：

public class ThreadDemo {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Demo d1 = new Demo("one1");
		Demo d2 = new Demo("two2");
		d1.start();
		d2.start();

		for (int i = 0; i < 20; i++) {
			System.out.println("main ==== "+i);
		}
	}
}

class Demo extends Thread{
	public Demo(String str) {
		// TODO Auto-generated constructor stub
		super(str);
	}
	
	public void run() {
	for (int i = 0; i < 20; i++) {
		System.out.println(this.getName()+" run---- "+i);
		}	
	}
}

执行结果如下：

main ==== 0
main ==== 1
main ==== 2
main ==== 3
one1 run---- 0
two2 run---- 0
two2 run---- 1
two2 run---- 2
two2 run---- 3
two2 run---- 4
two2 run---- 5
two2 run---- 6
two2 run---- 7
two2 run---- 8
two2 run---- 9
two2 run---- 10
two2 run---- 11
two2 run---- 12
two2 run---- 13
two2 run---- 14
two2 run---- 15
two2 run---- 16
two2 run---- 17
two2 run---- 18
one1 run---- 1
main ==== 4
main ==== 5
main ==== 6
main ==== 7
main ==== 8
one1 run---- 2
one1 run---- 3
one1 run---- 4
one1 run---- 5
one1 run---- 6
one1 run---- 7
two2 run---- 19
one1 run---- 8
main ==== 9
one1 run---- 9
main ==== 10
one1 run---- 10
main ==== 11
one1 run---- 11
main ==== 12
main ==== 13
one1 run---- 12
main ==== 14
main ==== 15
main ==== 16
main ==== 17
main ==== 18
main ==== 19
one1 run---- 13
one1 run---- 14
one1 run---- 15
one1 run---- 16
one1 run---- 17
one1 run---- 18
one1 run---- 19

获取当前执行的线程：currentThread()