一、 java线程状态到底几种？

线程状态网上各种奇葩文章描述5种的也有，7种的也有，这里告诉你：

JDK源码中Thread类内部有枚举类State详细描述了线程6种线程状态：
1.NEW:尚未启动；
2.RUNNABLE：运行中
3.BlOCKED：线程等待monitor锁定的状态（synchronized同步块中阻塞）
4.WAITING:等待线程，主动调用wait()、join()、park()后的状态
5.TIMED_WAITING:等待超时，Thead.sleep(long),wait(long),join(long),parkNanos (long),parkUntil
6.TERMINATED:线程终止

public enum State {/*** Thread state for a thread which has not yet started.*/NEW,/*** Thread state for a runnable thread.  A thread in the runnable* state is executing in the Java virtual machine but it may* be waiting for other resources from the operating system* such as processor.*/RUNNABLE,/*** Thread state for a thread blocked waiting for a monitor lock.* A thread in the blocked state is waiting for a monitor lock* to enter a synchronized block/method or* reenter a synchronized block/method after calling* {@link Object#wait() Object.wait}.*/BLOCKED,/*** Thread state for a waiting thread.* A thread is in the waiting state due to calling one of the* following methods:* <ul>*   <li>{@link Object#wait() Object.wait} with no timeout</li>*   <li>{@link #join() Thread.join} with no timeout</li>*   <li>{@link LockSupport#park() LockSupport.park}</li>* </ul>** <p>A thread in the waiting state is waiting for another thread to* perform a particular action.** For example, a thread that has called <tt>Object.wait()</tt>* on an object is waiting for another thread to call* <tt>Object.notify()</tt> or <tt>Object.notifyAll()</tt> on* that object. A thread that has called <tt>Thread.join()</tt>* is waiting for a specified thread to terminate.*/WAITING,/*** Thread state for a waiting thread with a specified waiting time.* A thread is in the timed waiting state due to calling one of* the following methods with a specified positive waiting time:* <ul>*   <li>{@link #sleep Thread.sleep}</li>*   <li>{@link Object#wait(long) Object.wait} with timeout</li>*   <li>{@link #join(long) Thread.join} with timeout</li>*   <li>{@link LockSupport#parkNanos LockSupport.parkNanos}</li>*   <li>{@link LockSupport#parkUntil LockSupport.parkUntil}</li>* </ul>*/TIMED_WAITING,/*** Thread state for a terminated thread.* The thread has completed execution.*/TERMINATED;}

二、 java线程状态的切换

线程切换代码示例：

package shen.example.demo.mutithread;import java.util.concurrent.locks.LockSupport;/*** 线程状态demo*/
public class ThreadStatusDemo {public static void main(String[] args) throws InterruptedException {//创建一个线程System.out.println("创建子线程new");Thread thread = new Thread(()->{//2.线程状态：RUNNABLESystem.out.println(Thread.currentThread().getState());System.out.println("子线程运行中...开始调用park()");LockSupport.park();//睡眠try {System.out.println("子线程运行中...调用sleep(long)");Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}//获取同步锁System.out.println("子线程运行中...进入同步代码块");synchronized (ThreadStatusDemo.class){try {Thread.sleep(500);} catch (InterruptedException e) {e.printStackTrace();}}});//1.线程状态：NEWSystem.out.println(thread.getState());System.out.println("子线程启动start");//启动线程thread.start();//主线程睡眠，等待子线程thread调用park()Thread.sleep(500);//3.线程状态：WAITINGThread.sleep(500);System.out.println(thread.getState());//唤醒子线程,使子线程调用sleep(long)LockSupport.unpark(thread);//4.TIMED_WAITINGSystem.out.println(thread.getState());//主线程获取当前类锁synchronized (ThreadStatusDemo.class){Thread.sleep(1200);//等待子线程进入同步代码块阻塞//5.BLOCKEDSystem.out.println(thread.getState());}Thread.sleep(1200);System.out.println("子线程运行结束");//5.TERMINATEDSystem.out.println(thread.getState());}
}

运行结果：

创建子线程new
NEW
子线程启动start
RUNNABLE
子线程运行中...开始调用park()
WAITING
子线程运行中...调用sleep(long)
TIMED_WAITING
子线程运行中...进入同步代码块
BLOCKED
子线程运行结束
TERMINATED