我的错误是 java.lang.NumberFormatException

Question

我正在使用 jcreator。它表示该过程已完成，但是当您切换到 case 4 然后选择数字 1-9 时，它表示 java.numberformatexception。是什么原因造成的，我该如何解决？我只是这里的初学者。

import javax.swing.JOptionPane;

public class Exer29A {

    public static String inputdialog(String s)
    {
        JOptionPane.showInputDialog(null,s);
        return s;
    }   
    static void messagedialog(String r) 
    {
        JOptionPane.showMessageDialog(null, r);
    }
    public static void main(String[] args) {
        int xx, x1, x2;
        String n1, n2, LName, MName, FName;
        FName = JOptionPane.showInputDialog(null, "What's your first name?");
        MName = JOptionPane.showInputDialog(null, "What's your Middle name?");
        LName = JOptionPane.showInputDialog(null, "What's your Last name?");
        n2 = JOptionPane.showInputDialog(null, "So you are " + FName.substring(0,1).toUpperCase() + FName.substring(1).toLowerCase() + " " + MName.substring(0,1).toUpperCase() + MName.substring(1).toLowerCase() + " " + LName.substring(0,1).toUpperCase() + LName.substring(1).toLowerCase() + " " + "Do you wish to continue?[Y/N]");

        if (n2.equalsIgnoreCase("Y"))
            {
                 x1 = Integer.parseInt(JOptionPane.showInputDialog(null, "What do you want to do? \n 1. Add 2 integers \n 2. Area of a rectangle \n 3. Area of a triangle \n 4. Know your fate.")); 
                    switch (x1)
                    {
                    case 1:
                    {
                        x1 = Integer.parseInt(JOptionPane.showInputDialog(null, "Enter 1st integer."));
                        x2 = Integer.parseInt(JOptionPane.showInputDialog(null, "Enter 2nd integer"));
                        messagedialog("The sum of two numbers is " + (x1+x2) );
                    }
                    break;
                    case 2:
                    {
                        x1 = Integer.parseInt(JOptionPane.showInputDialog(null, "Enter 1st integer."));
                        x2 = Integer.parseInt(JOptionPane.showInputDialog(null, "Enter 2nd integer"));
                        messagedialog("The area of the triangle is " + (x1*x2) );
                    }
                    break;
                    case 3:
                    {
                        x1 = Integer.parseInt(JOptionPane.showInputDialog(null, "Enter base."));
                        x2 = Integer.parseInt(JOptionPane.showInputDialog(null, "Enter height"));
                        messagedialog("The are of the triangle is " + ((double)(0.5*x1*x2)));
                    }
                    case 4:
                    {
                        xx = Integer.parseInt(inputdialog("Choose numbers 1-9"));
                    {

                            if (xx==1)
                                messagedialog("You will be successful!");
                            else if (xx==2)
                                messagedialog("You will have a beautiful life. Blessings would come to you.");
                            else if (xx==3)
                                messagedialog("You are handsome/gorgeous. But.....");
                            else if (xx==4)
                                messagedialog("You must study well.");
                            else if (xx==5)
                                messagedialog("Unfortunately, you are unfortunate.");
                            else if (xx==6)
                                messagedialog("You will be an environmentalist. You will be called the Keeper of the Forest.");
                            else if (xx==7)
                                messagedialog("You are nothing but luck. You will be poured out with luck.");
                            else if (xx==8)
                                messagedialog("8. Nothing but a number. Try again.");
                            else
                                messagedialog("Endowed with the gift to serve others, people with the lucky number 9 are able to freely create an easy and relaxed atmosphere. /n Your humanity is welcomed among their friends. Besides, they are brilliant, funny, smart and generous. ");    
                        }
                    }
                    break;
                    default:
                        messagedialog("invalid");
                    }
            }
        else if (n2.equalsIgnoreCase("N"))
            System.exit(0);
        else
            messagedialog("INVALID");

    }

}

异常堆栈跟踪：

Exception in thread "main" java.lang.NumberFormatException: For input string: "Choose numbers 1-9" 
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
    at java.lang.Integer.parseInt(Integer.java:580)
    at java.lang.Integer.parseInt(Integer.java:615)
    at Exer29A.main(Exer29A.java:50) 

Answer 1

与所有其他调用不同，对于案例“4”，您调用 inputDialog(...) 而不是 JOptionPane.showInputDialog(null, "Enter base.")。这不是主要问题。

主要问题是什么 inputDialog(...) 返回。这和JOptionPane.showInputDialog(null, "Enter base.") 返回的不是一回事。