Java多线程——之一创建线程的四种方法

Z时代
2024-01-10
分类：综合

1.实现Runnable接口，重载run()，无返回值


package thread;
public class ThreadRunnable implements Runnable {
  public void run() {
    for (int i = 0; i < 10; i++) {
      System.out.println(Thread.currentThread().getName() + ":" + i);
    }
  }
}
package thread;
public class ThreadMain {
  public static void main(String[] args) throws Exception {
    ThreadRunnable threadRunnable1 = new ThreadRunnable();
    ThreadRunnable threadRunnable2 = new ThreadRunnable();
    ThreadRunnable threadRunnable3 = new ThreadRunnable();
    ThreadRunnable threadRunnable4 = new ThreadRunnable();
    Thread thread1 = new Thread(threadRunnable1);
    Thread thread2 = new Thread(threadRunnable2);
    Thread thread3 = new Thread(threadRunnable3);
    Thread thread4 = new Thread(threadRunnable4);
    thread1.start();
    thread2.start();
    thread3.start();
    thread4.start();
  }
}

2.继承Thread类，复写run()

使用时通过调用Thread的start()（该方法是native），再调用创建线程的run()，不同线程的run方法里面的代码交替执行。

不足：由于java为单继承，若使用线程类已经有个父类，则不能使用该方式创建线程。


public class ThreadEx extends Thread {
  public void run() {
    for (int i = 0; i < 10; i++) {
      System.out.println(Thread.currentThread() + ":" + i);
    }
  }
}
public class ThreadMain {
  public static void main(String[] args)
  {
    ThreadEx threadEx = new ThreadEx();
    threadEx.start();
  }
}

3.实现Callable接口，通过FutureTask/Future来创建有返回值的Thread线程，通过Executor执行

补充：与实现Runnable接口类似，都是实现接口，不同的是该方式有返回值，可以获得异步执行的结果。

延伸：FutureTask是类，Future是接口。


package thread;
import java.util.concurrent.*;
public class ThreadCallable {
  public static void main(String[] args) throws Exception {
    FutureTask<Integer> futureTask = new FutureTask<Integer>(new Callable<Integer>() {
      public Integer call() throws Exception {
        for (int i = 0; i < 10; i++) {
          System.out.println(Thread.currentThread().getName() + ":" + i);
        }
        return 1;
      }
    });
    Executor executor = Executors.newFixedThreadPool(1);
    ((ExecutorService) executor).submit(futureTask);
    //获得线程执行状态
    System.out.println(Thread.currentThread().getName() + ":" + futureTask.get());
  }
}

4.使用Executors创建ExecutorService，入参Callable或Future

补充：适用于线程池和并发


package thread;
import java.util.concurrent.Callable;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import static java.lang.Thread.sleep;
public class ThreadExecutors {
  private final String threadName;
  public ThreadExecutors(String threadName) {
    this.threadName = threadName;
  }
  private ThreadFactory createThread() {
    ThreadFactory tf = new ThreadFactory() {
      public Thread newThread(Runnable r) {
        Thread thread = new Thread();
        thread.setName(threadName);
        thread.setDaemon(true);
        try {
          sleep(1000);
        }
        catch (InterruptedException e) {
          e.printStackTrace();
        }
        return thread;
      }
    };
    return tf;
  }
  public Object runCallable(Callable callable) {
    return Executors.newSingleThreadExecutor(createThread()).submit(callable);
  }
  public Object runFunture(Runnable runnable) {
    return Executors.newSingleThreadExecutor(createThread()).submit(runnable);
  }
}
package thread;
import java.util.concurrent.*;
public class ThreadMain {
  public static void main(String[] args) throws Exception {
    ThreadExecutors threadExecutors = new ThreadExecutors("callableThread");
    threadExecutors.runCallable(new Callable() {
      public String call() throws Exception {
        return "success";
      }
    });
    threadExecutors.runFunture(new Runnable() {
      public void run() {
        System.out.println("execute runnable thread.");
      }
    });
  }
}