具有Lambda表达式的线程

Question

我在第42和43行有一个错误:Thread t1=new Thread(()->prod.test());,Thread t2=new Thread(()->cons.test()); 未处理的异常类型InterruptedException.如果我尝试quickfix它将创建带有捕获异常的try catch ,它将具有相同的错误,并将尝试以相同的方式修复它,继续用try catch包围它.

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

interface Predicate {
    public void test() throws InterruptedException;
}

class MyClass {
    int num = 0;
    Lock lock = new ReentrantLock();

    public void produce() throws InterruptedException {
        lock.lock();
        for (int i = 0; i < 1000; i++) {
            num++;
            Thread.sleep(1);
        }
        lock.unlock();
    }

    public void consume() throws InterruptedException {
        lock.lock();
        for (int i = 0; i < 1000; i++) {
            num--;
            Thread.sleep(1);
        }
        lock.unlock();
    }

    public int getNum() {
        return num;
    }

}

public class Main00 {

    public static void main(String[] args) throws InterruptedException {
        MyClass c = new MyClass();
        Predicate prod = c::produce;
        Predicate cons = c::consume;
        Thread t1 = new Thread(() -> prod.test());
        Thread t2 = new Thread(() -> cons.test());
        long start = System.currentTimeMillis();
        t1.start();
        t2.start();
        t1.join();
        t2.join();
        long end = System.currentTimeMillis();
        System.out.println("time taken " + (end - start) + " num = "
                + c.getNum());
    }

}

Answer 1

您已经创建了一个功能接口,Predicate其方法被声明为throw InterruptedException,这是一个经过检查的异常.但是,您test()将lambda表达式的主体调用为构造函数的参数,该Thread构造函数采用aRunnable,其run()方法未声明为抛出任何已检查的异常.因此,由于异常未在正文中捕获,因此会发生编译器错误.

顺便说一下,Predicate由于功能方法返回的内置功能接口java.util.function.Predicate,命名您自己的接口可能会令人困惑boolean.

因为run()不能抛出Exception,你必须catch处理异常并处理它.您可以记录异常及其堆栈跟踪.您可以将异常包装在一个RuntimeException.无论哪种方式,捕获已检查的异常将允许代码编译.例:

Thread t1 = new Thread(() -> {
    try {
        prod.test();
    } catch (InterruptedException e) {
        // handle: log or throw in a wrapped RuntimeException
        throw new RuntimeException("InterruptedException caught in lambda", e);
    }
});

Answer 2

如果你打算只运行一个没有参数的方法，你可以用方法引用替换 lambda。

例如：

Thread t = new Thread(() -> {
        foo();
    });

可以更简洁地表示为

Thread t = new Thread(this::foo);