使用开关并尝试声明来验证用户输入

Question

我一直在这一点工作，它不会编译。它给了我一个错误说

变量的选择可能没有 初始化 开关（选择） ^

，但我在程序变量集。所以我不知道问题是什么？它是否真的能够避免编译？

import java.io.*; 
    import javax.swing.JOptionPane; 

    public class MyType 
    { 
     public static void main(String[] args) 
     { 
      String strChoice = "", strTryString, strTryInt, strTryDouble; 
      Integer choice, tryInt; 
      double tryDouble; 
      boolean done = false; 

      while(!done) 
     { 
       try 
       { 
        String answer = JOptionPane.showInputDialog(null, "What's my type\n\n\n1) String\n2) integer\n3) double\n4) Quit the program"); 
        choice = Integer.parseInt(strChoice); 

        //test for valid codes 1, 2, 3, or 4 
        if (choice<1 || choice>4) throw new NumberFormatException(); 
        else done = true; 
       } 
        catch(NumberFormatException e) 
       { 
        JOptionPane.showInputDialog(null, "Please enter a 1, 2, 3, or 4", "Error", JOptionPane.INFORMATION_MESSAGE); 
        switch(choice) 
       { 
         case 1: 
          JOptionPane.showMessageDialog(null, "Correct, any input can be saved as a String"); 
          break; 

         case 2: 
          JOptionPane.showMessageDialog(null, "Correct!"); 
          tryInt = Integer.parseInt(strChoice); 
          break; 

         case 3: 
          JOptionPane.showMessageDialog(null, "Correct!"); 
          tryDouble = Integer.parseInt(strChoice); 
          break; 

         case 4: 
          done = true; 
          JOptionPane.showMessageDialog(null, "Exit."); 
          System.exit(0); 
          break; 
         default: throw new NumberFormatException(); 
      } 
      } 

      } 
     } 
    } 

Answer 1

如果showInputDialog抛出，那么'choice'没有设置。

try 
      { 
       String answer = JOptionPane.showInputDialog(null, "What's my type\n\n\n1) String\n2) integer\n3) double\n4) Quit the program"); 
       choice = Integer.parseInt(strChoice); 

       //test for valid codes 1, 2, 3, or 4 
       if (choice<1 || choice>4) throw new NumberFormatException(); 
       else done = true; 
      } 
       catch(NumberFormatException e) 
      { 

Answer 2

你应该尝试块之前iniatialize选择的变量，因为你是在抓，在某些情况下，如果异常被选择happining那么varaible选择将未初始化的初始化之前扔引用它。