Scanner.NextInt上的InputMismatchException

Question

 Exception in thread "main" java.util.InputMismatchException
 at java.util.Scanner.throwFor(Unknown Source)
 at java.util.Scanner.next(Unknown Source)
 at java.util.Scanner.nextInt(Unknown Source)
 at java.util.Scanner.nextInt(Unknown Source)
 at DrawerAutoRect.main(DrawerAutoRect.java:39)

这个程序的目标是选择要绘制的对象类型，即：线条、矩形、o vals，然后输入参数，即如果我要绘制的是矩形，输入将是r，200，200，400，400，并在JFrame上绘制具有这些尺寸的矩形。然后输入“end”，等待对象输入和绘制就结束了。

import java.awt.BasicStroke;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.util.Scanner;
import javax.swing.JFrame;

public class DrawerAutoRect extends JFrame {
    public DrawerAutoRect(){
    setSize(1020,1020);
}

public static void paint(Graphics g, int a, int b,int c, int d)
{
   Graphics2D g2 = (Graphics2D)g;
   g2.drawRect(a, b, c, d);
}

public static void main(String[] args) {
    int x1 = 100;
    int x2 = 100;
    int y1 = 50;
    int y2 = 50;
    Scanner s = new Scanner(System.in);
    String dim = s.next();
    while(dim!="end"){
        if(dim.equals("r")){
            x1 = s.nextInt();
            y1 = s.nextInt();
            x2 = s.nextInt();
            y2 = s.nextInt();
        }
    }
    paint(null, x1, y1, x2, y2);
    DrawerAutoRect r = new DrawerAutoRect();
    r.setDefaultCloseOperation(EXIT_ON_CLOSE);
    r.setVisible(true);
    //r.pack();
    r.setTitle("Tutorial");
}

Answer 1

问题是，输入不仅包含要查找的标记，还包含逗号和空格。

因此，您必须告诉扫描器使用特定的分隔符，以理解他必须在这个字符串上标记您的输入流。

我建议您使用以下regex作为扫描程序的分隔符：

,\s*|\s+

null

try (final Scanner s = new Scanner(System.in)) {
    s.useDelimiter(",\\s*|\\s+");

    String dim;
    do {
        dim = s.next();
        if (dim.equals("r")) {
            System.out.println(s.nextInt());
            System.out.println(s.nextInt());
            System.out.println(s.nextInt());
            System.out.println(s.nextInt());
        }
    } while (!dim.equals("end"));
}

r 1, 2, 3, 4, end

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