Java 實現多線程的三種方式

Java 實現多線程的三種方式

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：實現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：實現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();
}
}

}

方法一，繼承自Thread

public class ThreadExtendsThread extends Thread {
private int i;
@Override
public void run() {
for(; i < 100; i++) {
System.out.println(getName() + " " + i);
}
}
}

run方法為線程執行體，ThreadExtendsThread對象即為線程對象。

方法二，實現Runnable接口

public class ThreadImplementsRunnable implements Runnable {
private int i;
@Override
public void run() {
for(; i < 100; i++){
System.out.println(Thread.currentThread().getName() + " " + i);
}
}
}

run方法為線程執行體，使用時New一個Thread對象，Runnable對象作為target傳遞給Thread對象。且同一個Runnable對象可作為多個Thread的target，這些線程均共享Runnable對象的實例變量。

方法三，實現Callable接口

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接口類似於Runnable接口，但比對方強大，線程執行體為call方法，該方法具有返回值和可拋出異常。使用時將Callable對象包裝為FutureTask對象，通過泛型指定返回值類型。可稍候調用FutureTask的get方法取回執行結果。