java - 使用空字符作为循环条件，程序在应该循环时结束

Question

This program is supposed to loop for an input of a char if nothing is written in, the program will however not compile, it does not accept char tegn='';. How can i create a loop where the condition si that nothing has been written in for a char?

import static javax.swing.JOptionPane.*;
       char tegn = '';
        do {
        tegn = showInputDialog("Input a char.").charAt(0);
        } while (tegn == '');

更新:我用 Vishal K 代码中的一个想法解决了我的代码，使用 String 来确定用户是否没有写入或写入了什么:

    String tegn = ""; 
do { tegn = showInputDialog("Input a char."); 
} while (tegn.equals("")); 

char chartegn = tegn.charAt(0);

Answer 1

您可以尝试以下操作:

import static javax.swing.JOptionPane.*;
    String str = "";
    char tegn=' ';
    do {
     str = showInputDialog("Input a char.");
     if (str != null && !"".equalsIgnoreCase(str.trim()))
     {
       tegn = str.charAt(0);
     }
    }while(str!=null && !"".equalsIgnoreCase(str.trim())