线程在其生命周期中会经历各个阶段。例如，一个线程诞生、启动、运行，然后消亡。下图展示了线程的完整生命周期。
以下是生命周期的各个阶段
New - 新线程在新状态下开始其生命周期。它保持这种状态直到程序启动线程。它也被称为出生线程。
Runnable - 新出生的线程启动后，该线程变得可运行。处于此状态的线程被认为正在执行其任务。
Running- 有时，线程在等待时会转换到等待状态另一个线程来执行任务。仅当另一个线程向等待线程发出继续执行的信号时，线程才会转换回可运行状态。
Waiting- 可运行线程可以进入指定时间间隔的定时等待状态。当该时间间隔到期或正在等待的事件发生时，处于此状态的线程将转换回可运行状态。
Dead - 可运行线程在完成其任务或以其他方式终止时进入终止状态。
示例 1
在此示例中，我们正在创建通过继承 Thread 类来创建两个线程。我们正在打印线程的每个状态。当线程对象被创建时，其状态为NEW；当调用start()方法时，状态为START；当run()方法被调用时，状态为RUNNING；当线程完成对 run() 方法的处理时，它会进入 DEAD 状态。
package com.yxjc123;
class ThreadDemo extends Thread {
private Thread t;
private String threadName;
ThreadDemo( String name) {
threadName = name;
System.out.println("Thread: " + threadName + ", " + "State: New");
}
public void run() {
System.out.println("Thread: " + threadName + ", " + "State: Running");
for(int i = 4; i > 0; i--) {
System.out.println("Thread: " + threadName + ", " + i);
}
System.out.println("Thread: " + threadName + ", " + "State: Dead");
}
public void start () {
System.out.println("Thread: " + threadName + ", " + "State: Start");
if (t == null) {
t = new Thread (this, threadName);
t.start ();
}
}
}
public class TestThread {
public static void main(String args[]) {
ThreadDemo thread1 = new ThreadDemo( "Thread-1");
ThreadDemo thread2 = new ThreadDemo( "Thread-2");
thread1.start();
thread2.start();
}
} 输出
Thread: Thread-1, State: New
Thread: Thread-2, State: New
Thread: Thread-1, State: Start
Thread: Thread-2, State: Start
Thread: Thread-1, State: Running
Thread: Thread-2, State: Running
Thread: Thread-2, 4
Thread: Thread-2, 3
Thread: Thread-2, 2
Thread: Thread-2, 1
Thread: Thread-2, State: Dead
Thread: Thread-1, 4
Thread: Thread-1, 3
Thread: Thread-1, 2
Thread: Thread-1, 1
Thread: Thread-1, State: Dead 示例 2
在这个示例中，我们'使用 sleep() 方法在处理中引入一些延迟并展示使用线程的并行处理的情况。我们通过继承 Thread 类来创建两个线程。我们正在打印线程的每个状态。当线程对象被创建时，其状态为NEW；当调用start()方法时，状态为START；当run()方法被调用时，状态为RUNNING；如果调用 sleep()，则线程进入 WAITING 状态；当线程完成对 run() 方法的处理时，它会进入 DEAD 状态。
package com.yxjc123;
class ThreadDemo extends Thread {
private Thread t;
private String threadName;
ThreadDemo( String name) {
threadName = name;
System.out.println("Thread: " + threadName + ", " + "State: New");
}
public void run() {
System.out.println("Thread: " + threadName + ", " + "State: Running");
try {
for(int i = 4; i > 0; i--) {
System.out.println("Thread: " + threadName + ", " + i);
//让线程休眠一段时间。
System.out.println("Thread: " + threadName + ", " + "State: Waiting");
Thread.sleep(50);
}
} catch (InterruptedException e) {
System.out.println("Thread " + threadName + " interrupted.");
}
System.out.println("Thread: " + threadName + ", " + "State: Dead");
}
public void start () {
System.out.println("Thread: " + threadName + ", " + "State: Start");
if (t == null) {
t = new Thread (this, threadName);
t.start ();
}
}
}
public class TestThread {
public static void main(String args[]) {
ThreadDemo thread1 = new ThreadDemo( "Thread-1");
ThreadDemo thread2 = new ThreadDemo( "Thread-2");
thread1.start();
thread2.start();
}
} 输出
Thread: Thread-1, State: New
Thread: Thread-2, State: New
Thread: Thread-1, State: Start
Thread: Thread-2, State: Start
Thread: Thread-1, State: Running
Thread: Thread-1, 4
Thread: Thread-1, State: Waiting
Thread: Thread-2, State: Running
Thread: Thread-2, 4
Thread: Thread-2, State: Waiting
Thread: Thread-1, 3
Thread: Thread-2, 3
Thread: Thread-2, State: Waiting
Thread: Thread-1, State: Waiting
Thread: Thread-2, 2
Thread: Thread-1, 2
Thread: Thread-1, State: Waiting
Thread: Thread-2, State: Waiting
Thread: Thread-2, 1
Thread: Thread-2, State: Waiting
Thread: Thread-1, 1
Thread: Thread-1, State: Waiting
Thread: Thread-2, State: Dead
Thread: Thread-1, State: Dead 示例 3
在这个示例中，我们通过实现 Runnable 接口来创建两个线程。我们正在打印线程的每个状态。当线程对象被创建时，其状态为NEW；当调用start()方法时，状态为START；当run()方法被调用时，状态为RUNNING；如果调用 sleep()，则线程进入 WAITING 状态；当线程处理完 run() 方法后，它就进入 DEAD 状态。
package com.yxjc123;
class ThreadDemo implements Runnable {
private Thread t;
private String threadName;
ThreadDemo( String name) {
threadName = name;
System.out.println("Thread: " + threadName + ", " + "State: New");
}
public void run() {
System.out.println("Thread: " + threadName + ", " + "State: Running");
try {
for(int i = 4; i > 0; i--) {
System.out.println("Thread: " + threadName + ", " + i);
//让线程休眠一段时间。
System.out.println("Thread: " + threadName + ", " + "State: Waiting");
Thread.sleep(50);
}
} catch (InterruptedException e) {
System.out.println("Thread " + threadName + " interrupted.");
}
System.out.println("Thread: " + threadName + ", " + "State: Dead");
}
public void start () {
System.out.println("Thread: " + threadName + ", " + "State: Start");
if (t == null) {
t = new Thread (this, threadName);
t.start ();
}
}
}
public class TestThread {
public static void main(String args[]) {
ThreadDemo thread1 = new ThreadDemo( "Thread-1");
ThreadDemo thread2 = new ThreadDemo( "Thread-2");
thread1.start();
thread2.start();
}
} 输出
Thread: Thread-1, State: New
Thread: Thread-2, State: New
Thread: Thread-1, State: Start
Thread: Thread-2, State: Start
Thread: Thread-1, State: Running
Thread: Thread-1, 4
Thread: Thread-1, State: Waiting
Thread: Thread-2, State: Running
Thread: Thread-2, 4
Thread: Thread-2, State: Waiting
Thread: Thread-1, 3
Thread: Thread-2, 3
Thread: Thread-2, State: Waiting
Thread: Thread-1, State: Waiting
Thread: Thread-2, 2
Thread: Thread-1, 2
Thread: Thread-1, State: Waiting
Thread: Thread-2, State: Waiting
Thread: Thread-2, 1
Thread: Thread-2, State: Waiting
Thread: Thread-1, 1
Thread: Thread-1, State: Waiting
Thread: Thread-2, State: Dead
Thread: Thread-1, State: Dead