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Java 实现多线程的三种方式


 

import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;

public class Main {

    public static void main(String[] args) {
        //方法一:继承Thread
        int i = 0;
//        for(; i < 100; i++){
//            System.out.println(Thread.currentThread().getName() + " " + i);
//            if (i == 5) {
//                ThreadExtendsThread threadExtendsThread = new ThreadExtendsThread();
//                threadExtendsThread.start();
//            }
//        }
       
        //方法二:实现Runnable
//        for(i = 0; i < 100; i++){
//            System.out.println(Thread.currentThread().getName() + " " + i);
//            if (i == 5) {
//                Runnable runnable = new ThreadImplementsRunnable();
//                new Thread(runnable).start();
//                new Thread(runnable).start();
//            }
//        }

        //方法三:实现Callable接口
        Callable<Integer> callable = new ThreadImplementsCallable();
        FutureTask<Integer> futureTask = new FutureTask<>(callable);
        for(i = 0; i < 100; i++){
            System.out.println(Thread.currentThread().getName() + " " + i);
            if (i == 5) {
                new Thread(futureTask).start();
                new Thread(futureTask).start();
            }
        }
        try {
            System.out.println("futureTask ruturn: " + futureTask.get());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}
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方法一,继承自Thread

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public class ThreadExtendsThread extends Thread {
    private int i;
    @Override
    public void run() {
        for(; i < 100; i++) {
            System.out.println(getName() + " " + i);
        }
    }
}
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run方法为线程执行体,ThreadExtendsThread对象即为线程对象。

方法二,实现Runnable接口

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public class ThreadImplementsRunnable implements Runnable {
    private int i;
    @Override
    public void run() {
        for(; i < 100; i++){
            System.out.println(Thread.currentThread().getName() + " " + i);
        }
    }
}
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run方法为线程执行体,使用时New一个Thread对象,Runnable对象作为target传递给Thread对象。且同一个Runnable对象可作为多个Thread的target,这些线程均共享Runnable对象的实例变量。

方法三,实现Callable接口

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import java.util.concurrent.Callable;

public class ThreadImplementsCallable implements Callable<Integer> {
    private int i;
   
    @Override
    public Integer call() throws Exception {
        for(; i < 100; i++){
            System.out.println(Thread.currentThread().getName() + " " + i);
        }
        return i;
    }
}
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Callable接口类似于Runnable接口,但比对方强大,线程执行体为call方法,该方法具有返回值和可抛出异常。使用时将Callable对象包装为FutureTask对象,通过泛型指定返回值类型。可稍候调用FutureTask的get方法取回执行结果。