我们先来看段示例代码
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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(); } }} |
接下来我们来详细探讨下Java 实现多线程的几种方式
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); } }} |
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); } }} |
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; }} |
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。
