Runnable和Callable有什么区别？

主要区别

• Runnable 接口 run 方法无返回值；Callable 接口 call 方法有返回值，支持泛型
• Runnable 接口 run 方法只能抛出运行时异常，且无法捕获处理；Callable 接口 call 方法允许抛出异常，可以获取异常信息

测试代码

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;
 
public class TestRunnableAndCallable {
 
    public static void main(String[] args) {
        testImplementsRunable();
        testImplementsCallable();
        testImplementsCallableWithException();
    }
    
    //测试实现Runnable接口的方式创建、启动线程
    public static void testImplementsRunable() {
        Thread t1 = new Thread(new CustomRunnable());
        t1.setName("CustomRunnable");
        t1.start();
    }
    
    //测试实现Callable接口的方式创建、启动线程
    public static void testImplementsCallable() {
        Callable<String> callable = new CustomCallable();
        FutureTask<String> futureTask = new FutureTask<String>(callable);
        Thread t2 = new Thread(futureTask);
        t2.setName("CustomCallable");
        t2.start();
        try {
            System.out.println(futureTask.get());
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
    }
    
    //测试实现Callable接口的方式创建、启动线程，抛出异常
    public static void testImplementsCallableWithException() {
        Callable<String> callable = new CustomCallable2();
        FutureTask<String> futureTask = new FutureTask<String>(callable);
        Thread t3 = new Thread(futureTask);
        t3.setName("CustomCallableWithException");
        t3.start();
        try {
            System.out.println(futureTask.get());
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
    }
    
}
 
//实现Runnable接口，重写run方法
class CustomRunnable implements Runnable {
 
    public void run() {
        System.out.println(Thread.currentThread().getName());
//        throw new RuntimeException("aaa");
    }
    
}
 
//实现Callable接口，重写call方法
class CustomCallable implements Callable<String> {
 
    public String call() throws Exception {
        System.out.println(Thread.currentThread().getName());
        return "Callable Result";
    }
    
}
 
//实现Callable接口，重写call方法无法计算抛出异常
class CustomCallable2 implements Callable<String> {
 
    public String call() throws Exception {
        System.out.println(Thread.currentThread().getName());
        throw new Exception("I can compute a result");
    }
    
}

打印结果

CustomRunnable
CustomCallable
Callable Result
CustomCallableWithException
java.util.concurrent.ExecutionException: java.lang.Exception: I can compute a result
	at java.util.concurrent.FutureTask.report(FutureTask.java:122)
	at java.util.concurrent.FutureTask.get(FutureTask.java:192)
	at constxiong.interview.TestRunnableAndCallable.testImplementsCallableWithException(TestRunnableAndCallable.java:46)
	at constxiong.interview.TestRunnableAndCallable.main(TestRunnableAndCallable.java:12)
Caused by: java.lang.Exception: I can compute a result
	at constxiong.interview.CustomCallable2.call(TestRunnableAndCallable.java:81)
	at constxiong.interview.CustomCallable2.call(TestRunnableAndCallable.java:1)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.lang.Thread.run(Thread.java:748)

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