我的错误是java.lang.NumberFormatException

我正在使用jcreator。它表示该过程已完成，但当您转到切换，然后选择案例4，然后选择数字1-9时，它表示java.numberformatexception。这是什么原因造成的？我如何修复它？我只是个初学者

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) 

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与所有其他调用不同，对于案例“4”，您调用inputDialog。。。输入base，而不是JOptionPane.showInputDialognull。。这不是主要问题

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主要问题是什么输入对话框。。。返回。这与JOptionPane.showInputDialognull中输入base的内容不同。返回。

数字格式异常发生在哪里？3和4之间没有中断，不确定这是否是故意的。您对此条件的输入是什么？您的错误实际上是java.lang.NumberFormatException。必须准确报告错误消息、异常以及所有程序输出。您应该在问题中包含整个堆栈跟踪，不仅仅是一些与源代码不相关的错误消息的损坏版本。线程主java.lang.NumberFormatException中的异常：对于输入字符串：在java.lang.NumberFormatException.forInputStringNumberFormatException.java:65在java.lang.Integer.parseIntInteger.java:580在java:615在Exer29A.mainPer29a.java:50它会问你的名字，然后选择你想做什么，如果你选择4知道你的命运，然后选择数字1-9，然后消息就会弹出。它不会在InputDialog调用JOptionPane.showInputDialognull，s中输出我的if-else语句；并像所有其他字符串一样返回一个字符串…@MadProgrammer这是真的，但它返回哪个字符串？请不要回答这个问题。我会试着改变的。等等。哇。案件得到解决。谢谢各位。Im在用户定义的方法方面确实有困难。我们必须使用它。无论如何。上帝保佑@pcolor基本上是在编程过程中进行的；一切都会在一个方法中。所以现在犯错误是可以的，只要你从这些错误中吸取教训，你就可以在未来的几个月和几年里为自己省下很多痛苦。