小编T4l*_*l0n的帖子

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--; …

给定一个带有默认方法的简单接口:

private interface A {
    default void hello() {
        System.out.println("A");
    }
}

并且接受它的实例的方法:

private static void print(A a) {
    a.hello();
}

我可以使用匿名类覆盖它:

print(new A() {
    @Override
        public void hello() {
        System.out.println("OverHello");
    }
});

但如果我尝试使用lambda print(() -> System.out.println("OverHello2"));,我会收到编译错误.

找不到目标方法

有没有办法用lambda进行覆盖？

我想要一个简单的程序,用滑块改变矩形的宽度.当我运行它时,jpanel无法正常工作,因为它只适合panel.width宽度,并且不能正确重新绘制.

import java.awt.*;
import javax.swing.*;

public class panel extends JPanel {

    private int width = 50;

    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.setColor(Color.GRAY);
        g.fillRect(20, 20, width, 25);
    }

    public void setWidth(int width) {
        this.width = (width > 0) ? width : 0;
        repaint();
    }

    public int getWidth() {
        return width;
    }
}

GUI:

import java.awt.*;

import javax.swing.*;
import javax.swing.event.*;

public class Gui extends JFrame {

    private panel p;
    private JSlider slider;

    Gui() {
        super("Draw program");
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        p = new panel(); …

在这个例子中

Stream<MyClass>stream = Stream.of(new MyClass(5),new MyClass(15),new MyClass(8),new MyClass(12));

Map<Boolean, List<Integer>> map =
        stream.collect(Collectors.partitioningBy(a->a.getNum()<10));

在stream.collect检索地图布尔并List<MyClass>因此它不工作.我应该怎么做才能回到地图Boolean和List<Integer>呢？

我使用a ExecutorService有多个线程将文本写入文件,但我无法设法同步run()方法,而不是正确的逐行字符串我问,我有一个字符串的所有字符的混合,因为他们写它同时.

import java.io.BufferedReader
...

class WriteDns implements Runnable {

File file;
String text;

WriteDns(File file, String text) {
    this.file = file;
    this.text = text;
}

public void run() {
    synchronized (this) {
        try (BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(
                new FileOutputStream(file)))) {
            bw.write(turnDns() + "\n");
        } catch (IOException e) {
            System.out.println("Error");
        }
    }
}

public String turnDns() {
    int space = text.indexOf(' ');
    String ip = text.substring(0, space);
    String theRest = text.substring(space);
    String temp = ip; …