如何在java中使用goto语句？ [英] How to use goto statement in java?

问题描述

我已经用java编写了代码。并需要在其中使用goto语句。我已经在不同的论坛检查了解决方案并找到了使用break标签的解决方案：声明，但即使我在程序中描述标签也会出错。

Hi, I've written a code in java. and need to use goto statement in it. I've checked for the solutions at different forums and came to solutions of using break label: statement but it gives error even I describe the label in my program like.

break label:
..........
.........
label:

我正在尝试的代码是

The code I'm trying is

import javax.swing.JOptionPane;

/**
 *
 * @author hitman
 */
public class TestApp {
    
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        int tries = 3;
        String[] loginData;
        loginData = new String[100];
        short loginDataIndex = 0;
        
        do{
            String name;
            name = JOptionPane.showInputDialog("Enter Username");
            String pass = JOptionPane.showInputDialog("Enter Paswword");
            String captcha = JOptionPane.showInputDialog("3 * 6 = ");
            int captchaAnswer = Integer.parseInt(captcha);
            switch(captchaAnswer){
                case 18:
                 JOptionPane.showMessageDialog(null,"You are a Human","Login Sucessfull",JOptionPane.INFORMATION_MESSAGE);
                 break label:  // instead of goto
                 break;
                default:
                     JOptionPane.showMessageDialog(null,"You are not a Human", "Login Failed",JOptionPane.ERROR_MESSAGE);

            }
            loginData[loginDataIndex] = name;
            loginDataIndex++;
            --tries;
            JOptionPane.showMessageDialog(null,"You are Left with "+tries+" tries.","Tries Left",JOptionPane.WARNING_MESSAGE);
            
        }while(tries>0);
        label: //catches the break label statement
       
        JOptionPane.showMessageDialog(null,"Thanks for Visiting","Disabled",JOptionPane.INFORMATION_MESSAGE);
       if(loginData != null){
            short i = 0;
            String failedUsers = "";
            int n=0;
            while(loginData[n]!=null){
                failedUsers = failedUsers +" , "+loginData[n];
                n++;
            }
       
        JOptionPane.showMessageDialog(null,"Users "+failedUsers+" are not Human.","Captcha Error",JOptionPane.ERROR_MESSAGE);
       }
        System.exit(0);
        }
        
    }

推荐答案

不，你不需要它。如果您觉得自己需要它，请尝试训练自己，以提高您的代码编写技巧。 Java缺少goto声明：

http://docs.oracle .com / javase / tutorial / java / nutsandbolts / _keywords.html [ ^ ]。



即使没有使用const和goto，它们也是保留的。这意味着语法会阻止使用它作为标识符。

-SA

No, you don't need it. If you feel you need it, please try to train yourself to improve your code-writing skills just a bit more. Java lacks "goto" statement:
http://docs.oracle.com/javase/tutorial/java/nutsandbolts/_keywords.html[^].

Not that even though "const" and "goto" are not used, they are reserved. It means that syntax prevents using then even as identifiers.

—SA

设置标签在你的do-while循环之上：

Set the label above your do-while loop:

label: //catches the break label statement
        do{
            String name;
            name = JOptionPane.showInputDialog("Enter Username");
            String pass = JOptionPane.showInputDialog("Enter Paswword");
            String captcha = JOptionPane.showInputDialog("3 * 6 = ");
            int captchaAnswer = Integer.parseInt(captcha);
            switch(captchaAnswer){
                case 18:
                 JOptionPane.showMessageDialog(null,"You are a Human","Login Sucessfull",JOptionPane.INFORMATION_MESSAGE);
                 break label;  // instead of goto
                default:
                     JOptionPane.showMessageDialog(null,"You are not a Human", "Login Failed",JOptionPane.ERROR_MESSAGE);

            }
            loginData[loginDataIndex] = name;
            loginDataIndex++;
            --tries;
            JOptionPane.showMessageDialog(null,"You are Left with "+tries+" tries.","Tries Left",JOptionPane.WARNING_MESSAGE);

        }while(tries>0);

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