线程如何创建
创建线程有三种方式：继承Thread类；无返回值的Runnable；有返回值的Callable
示例如下
package com.rcl.platform.demo;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;
public class CreateThread {
public static class TestThread extends Thread {
@Override
public void run() {
System.out.println("--继承thread--");
}
}
public static class TestRunnable implements Runnable {
@Override
public void run() {
System.out.println("--runnable没有返回值--");
}
}
public static class TestCallable implements Callable<String> {
@Override
public String call() throws Exception {
System.out.println("--callable有返回值--");
return "test-callable";
}
}
public static void main(String[] args) throws InterruptedException, ExecutionException {
Thread thread = new Thread(new TestThread());
thread.start();
thread = new Thread(new TestRunnable());
thread.start();
FutureTask<String> ft = new FutureTask<>(new TestCallable());
thread = new Thread(ft);
thread.start();
System.out.println(ft.get());
}
}
执行结果
--继承thread-- --runnable没有返回值-- --callable有返回值-- test-callable
线程相关的基础方法
wait：获取锁对象monitor的线程执行wait方法，将会释放对monitor的控制权，其他线程可以获取到锁对象的monitor，执行notify唤醒wait线程
notify/notifyall：获取到monitor，唤醒曾经获取到monitor执行wait正在处于等待的线程（线程状态为WAITING，TIMED_WAITING）
sleep：线程休眠
yield：yield方法的作用是暂停当前线程，以便其他线程有机会执行，不过不能指定暂停的时间，并且也不能保证当前线程马上停止。yield方法只是将Running状态转变为Runnable状态（不能完全保证，最好少用）
join：join方法的作用是父线程等待子线程执行完成后再执行，换句话说就是将异步执行的线程合并为同步的线程，如：如果在mian线程执行的过程中执行t1.join方法，那么将转而执行t1线程，t1线程执行完毕后执行mian线程
package com.rcl.platform.demo;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;
public class JoinTest {
public static class TestThread extends Thread {
@Override
public void run() {
for(int i=0; i<10; i++){
System.out.println("第" + i + "次执行");
try {
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
public static void main(String[] args) throws InterruptedException, ExecutionException {
TestThread thread = new TestThread();
thread.start();
thread.join();
System.out.println("等待thread执行完毕后main线程结束");
}
}
执行结果
第0次执行 第1次执行 第2次执行 第3次执行 第4次执行 第5次执行 第6次执行 第7次执行 第8次执行 第9次执行 等待thread执行完毕后main线程结束
interrupt：他的作用是“停止”当前线程的运行，为什么加上一个引号，它只在特殊情况下有用，像线程调用了wait,sleep,join等可中断的阻塞方法 后，调用interrupt就会抛出InterruptedException异常。其实它称为协作停止。调用了这个方法后线程除了特殊情况外别的时候并不会停止，它发送一个停止请求，并且由线程记录下来（实际上就是有一个为bool的变量，当为true时就表示有停止线程运行请求）。所以说线程真正的停止需要我们自己去检查是否有停止线程的请求，当有线程停止请求时停用当前线程。和他配套是使用的有
public static boolean interrupted()
public boolean isInterrupted()
package com.rcl.platform.demo;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;
public class JoinTest {
public static class TestThread extends Thread {
@Override
public void run() {
for(int i=0; i<1000000000; i++){
System.out.println("TestThread第" + i + "次执行");
if(Thread.interrupted()){
return;
}
}
}
}
public static class TestThreadSleep extends Thread {
@Override
public void run() {
for(int i=0; i<10; i++){
System.out.println("TestThreadSleep第" + i + "次执行");
try {
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
if(Thread.interrupted()){
return;
}
}
}
}
public static void main(String[] args) throws InterruptedException, ExecutionException {
TestThread thread = new TestThread();
thread.start();
thread.interrupt();
TestThreadSleep threadSleep = new TestThreadSleep();
threadSleep.start();
threadSleep.interrupt();
}
}
执行结果
TestThread第0次执行
TestThreadSleep第0次执行
java.lang.InterruptedException: sleep interruptedTestThreadSleep第1次执行
at java.lang.Thread.sleep(Native Method)
at java.lang.Thread.sleep(Thread.java:340)
at java.util.concurrent.TimeUnit.sleep(TimeUnit.java:386)
at com.rcl.platform.demo.JoinTest$TestThreadSleep.run(JoinTest.java:27)
TestThreadSleep第2次执行
TestThreadSleep第3次执行
TestThreadSleep第4次执行
TestThreadSleep第5次执行
TestThreadSleep第6次执行
TestThreadSleep第7次执行
TestThreadSleep第8次执行
TestThreadSleep第9次执行
线程状态
1、java线程有6中状态，分别为NEW，RUNNABLE，BLOCKED，WAITING，TIMED_WAITING，TERMINATED详解java.lang.Thread$State枚举类
2、线程初始化为NEW状态，该状态表示还未调用start方法
3、执行线程调用start方法，线程状态转换为RUNNABLE（包括竞争到CPU时间真正意义的执行和没有竞争到CPU时间等待下一个CPU时间的状态）
4、BLOCKED状态为锁竞争，没有竞争到锁为BLOCKED，等待拥有锁的线程释放锁，进入RUNNABLE状态
5、WAITING状态为竞争到锁，执行wait方法，又释放锁，本线程进入WAITING，等待其他线程唤醒notify，notifyall，如果不唤醒，将一直处于WAITING状态
6、TIMED_WAITING为执行sleep join或者有时限的等待
7、线程执行完毕，线程处于TERMINATED状态
线程状态变化
package com.rcl.platform.demo;
import java.util.concurrent.TimeUnit;
public class ThreadState {
public static void main( String[] args ) throws InterruptedException {
System.out.println("-------------NEW-------------");
Thread thread = new Thread();
System.out.println(thread.getState() + ":" + (thread.getState() == Thread.State.NEW));
System.out.println("-------------分割线-------------");
System.out.println("-------------RUNNABLE、TERMINATED-------------");
thread = new Thread(new Runnable() {
public void run() {
System.out.println(Thread.currentThread().getState() + ":" + (Thread.currentThread().getState() == Thread.State.RUNNABLE));
}
});
thread.start();
TimeUnit.SECONDS.sleep(1);
System.out.println(thread.getState() + ":" + (thread.getState() == Thread.State.TERMINATED));
System.out.println("-------------分割线-------------");
System.out.println("-------------RUNNABLE、TIMED_WAITING-------------");
thread = new Thread(new Runnable() {
public void run() {
System.out.println(Thread.currentThread().getState() + ":" + (Thread.currentThread().getState() == Thread.State.RUNNABLE));
System.out.println("sleep 进入 TIMED_WAITING");
try {
TimeUnit.SECONDS.sleep(2);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
thread.start();
TimeUnit.SECONDS.sleep(1);
System.out.println(thread.getState() );
TimeUnit.SECONDS.sleep(2);
System.out.println("-------------分割线-------------");
System.out.println("-------------RUNNABLE、TIMED_WAITING-------------");
final Thread mainThread = Thread.currentThread();
thread = new Thread(new Runnable() {
public void run() {
System.out.println(Thread.currentThread().getState() + ":" + (Thread.currentThread().getState() == Thread.State.RUNNABLE));
try {
System.out.println("join 进入 TIMED_WAITING");
System.out.println("mainThread: " + mainThread.getState());
TimeUnit.SECONDS.timedJoin(mainThread, 2);//先执行mainthread
System.out.println("mainThread: " + mainThread.getState());
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
thread.start();
TimeUnit.SECONDS.sleep(1);
System.out.println("testThread: " + thread.getState() );
System.out.println("-------------分割线-------------");
System.out.println("-------------RUNNABLE、WAITING-------------");
Object lock = new Object();
final Thread mainThread1 = Thread.currentThread();
thread = new Thread(new Runnable() {
public void run() {
synchronized (lock) {
try {
System.out.println("wait 进入 WAITING");
lock.wait();
System.out.println("mainThread1: " + mainThread1.getState() );
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
});
thread.start();
TimeUnit.SECONDS.sleep(1);
System.out.println("testThread: " + thread.getState() );
synchronized (lock) {
lock.notifyAll();
}
TimeUnit.SECONDS.sleep(1);
System.out.println("-------------分割线-------------");
Thread thread1 = new Thread(new Runnable() {
public void run() {
synchronized (lock) {
try {
TimeUnit.SECONDS.sleep(2);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
});
thread1.start();
Thread thread2 = new Thread(new Runnable() {
public void run() {
synchronized (lock) {
}
}
});
thread2.start();
TimeUnit.SECONDS.sleep(1);
System.out.println("thread2: " + thread2.getState() );
}
}
执行结果
-------------NEW------------- NEW:true -------------分割线------------- -------------RUNNABLE、TERMINATED------------- RUNNABLE:true TERMINATED:true -------------分割线------------- -------------RUNNABLE、TIMED_WAITING------------- RUNNABLE:true sleep 进入 TIMED_WAITING TIMED_WAITING -------------分割线------------- -------------RUNNABLE、TIMED_WAITING------------- RUNNABLE:true join 进入 TIMED_WAITING mainThread: TIMED_WAITING testThread: TIMED_WAITING -------------分割线------------- -------------RUNNABLE、WAITING------------- wait 进入 WAITING mainThread: TIMED_WAITING testThread: WAITING mainThread1: TIMED_WAITING -------------分割线------------- thread2: BLOCKED
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时间： 2024-08-28 15:03:05