我們先來(lái)看段示例代碼
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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：繼承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：實(shí)現(xiàn)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：實(shí)現(xiàn)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(); } }} |
接下來(lái)我們來(lái)詳細(xì)探討下Java 實(shí)現(xiàn)多線程的幾種方式
方法一，繼承自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方法為線程執(zhí)行體，ThreadExtendsThread對(duì)象即為線程對(duì)象。
方法二，實(shí)現(xiàn)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方法為線程執(zhí)行體，使用時(shí)New一個(gè)Thread對(duì)象，Runnable對(duì)象作為target傳遞給Thread對(duì)象。且同一個(gè)Runnable對(duì)象可作為多個(gè)Thread的target，這些線程均共享Runnable對(duì)象的實(shí)例變量。
方法三，實(shí)現(xiàn)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接口類似于Runnable接口，但比對(duì)方強(qiáng)大，線程執(zhí)行體為call方法，該方法具有返回值和可拋出異常。使用時(shí)將Callable對(duì)象包裝為FutureTask對(duì)象，通過(guò)泛型指定返回值類型。可稍候調(diào)用FutureTask的get方法取回執(zhí)行結(jié)果。
