我们先来看段示例代码
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
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
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
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。
