参考 Java核心技术系列：Java多线程编程核心技术
1. currentThread方法
public class MyThread extends Thread {
public MyThread() {
System.out.println("MyThread.MyThread: "+MyThread.currentThread().getName());
}
@Override
public void run() {
System.out.println("run: "+ MyThread.currentThread().getName());
}
}
public class Demo01 {
public static void main(String[] args) {
MyThread run = new MyThread();
run.start();
}
}
输出结果如下：
MyThread.MyThread: main --> run对象创建是main线程
run: Thread-0 --> run方法执行是自己启动的线程
public class CountOperate extends Thread {
public CountOperate() {
System.out.println("CountOperate -------- begin");
System.out.println("name: "+Thread.currentThread().getName());
System.out.println("this.getName():" + this.getName());
System.out.println("CountOperate -------- end");
}
@Override
public void run() {
System.out.println("run -------- begin");
System.out.println("threadName: "+Thread.currentThread().getName());
System.out.println("this.getName():" + this.getName());
System.out.println("run -------- end");
}
}
public static void main(String[] args) throws InterruptedException {
CountOperate run = new CountOperate();
Thread thread = new Thread(run);
thread.setName("a");
thread.start();
/*run.setName("b");
run.start();*/
}
输出结果如下：
CountOperate -------- begin
name: main
this.getName():Thread-0
CountOperate -------- end
run -------- begin
threadName: a
this.getName():Thread-0
run -------- end
改变main方法代码如下：
public static void main(String[] args) {
CountOperate run = new CountOperate();
/*Thread thread = new Thread(run);
thread.setName("a");
thread.start();*/
run.setName("b");
run.start();
}
输出结果如下：
CountOperate -------- begin
name: main
this.getName():Thread-0
CountOperate -------- end
run -------- begin
threadName: b
this.getName():b
run -------- end
造成两个结果不一样的原因：Thread.currentThread()和this的区别
2. isAlive
public class MyThread extends Thread {
@Override
public void run() {
System.out.println("run: "+ this.isAlive());
}
}
public static void main(String[] args) {
MyThread run = new MyThread();
//MyThread t = new MyThread();
//Thread run = new Thread(t);
System.out.println(run.isAlive());//false
run.setName("b");
run.start();
System.out.println(run.isAlive());//true run还没有执行完毕
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(run.isAlive());//false
}
输出结果如下：
false --> 线程尚未启动
true --> run线程还没有执行完毕
run: true --> 执行MyThread线程里面run方法
false --> run线程在1s内执行完毕了
修改main方法代码如下：
public static void main(String[] args) {
//MyThread run = new MyThread();
MyThread t = new MyThread();
Thread run = new Thread(t);
System.out.println(run.isAlive());//false
run.setName("b");
run.start();
System.out.println(run.isAlive());//true run还没有执行完毕
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(run.isAlive());//false run在1s内执行完毕了
}
输出结果如下：
false
true
run: false 和之前的唯一区别：Thread.currentThread()和this的区别
false
更复杂的示例：
public class CountOperate extends Thread {
public CountOperate() {
System.out.println("CountOperate -------- begin");
System.out.println("thread: " + Thread.currentThread().getName());//thread: main
System.out.println("thread-isAlive: " + Thread.currentThread().isAlive());//thread-isAlive: true
System.out.println("this.getName():" + this.getName());//this.getName():Thread-0
System.out.println("this.isAlive:" + this.isAlive());//this.isAlive:false
System.out.println("CountOperate -------- end");
}
@Override
public void run() {
System.out.println("run -------- begin");
System.out.println("thread: " + Thread.currentThread().getName());//thread: b
System.out.println("thread-isAlive: " + Thread.currentThread().isAlive());//thread-isAlive: true
System.out.println("this.getName():" + this.getName());//this.getName():Thread-0
System.out.println("this.isAlive:" + this.isAlive());//this.isAlive:false
System.out.println("run -------- end");
}
}
public static void main(String[] args) {
//CountOperate run = new CountOperate();
CountOperate t = new CountOperate();
Thread run = new Thread(t);
System.out.println(run.isAlive());//false
run.setName("b");
run.start();
System.out.println(run.isAlive());//true run还没有执行完毕
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(run.isAlive());//false run在1s内执行完毕了
}
输出结果如下：
CountOperate -------- begin
thread: main
thread-isAlive: true
this.getName():Thread-0
this.isAlive:false
CountOperate -------- end
false
true
run -------- begin
thread: b
thread-isAlive: true
this.getName():Thread-0
this.isAlive:false
run -------- end
false
修改main方法代码如下：
public static void main(String[] args) {
CountOperate run = new CountOperate();
//CountOperate t = new CountOperate();
//Thread run = new Thread(t);
System.out.println(run.isAlive());//false
run.setName("b");
run.start();
System.out.println(run.isAlive());//true run还没有执行完毕
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(run.isAlive());//false run在1s内执行完毕了
}
输出结果如下：
CountOperate -------- begin
thread: main
thread-isAlive: true
this.getName():Thread-0
this.isAlive:false
CountOperate -------- end
false
true
run -------- begin
thread: b
thread-isAlive: true
this.getName():b
this.isAlive:true
run -------- end
false
3. sleep() 略去
在指定的毫秒数内让"当前正在执行的线程" 休眠(暂停执行)
当前正在执行的线程:是指 this.currentThread返回的线程