Java 错误，重复的局部变量 [英] Java error, duplicate local variable

问题描述

我正在尝试调试分配的一部分代码(我对 Java 还是很陌生)并且已经梳理了许多资源来解决这个冲突，但仍然不能完全解决.

I'm trying to debug a portion of code for an assignment (I'm still very new to Java) and have combed through many resources to solve this conflict but still can't quite work it out.

public static void main(String [] args){
    Scanner keyboard = new Scanner(System.in);
    String input = null;
    do
    {
      System.out.println("Enter 'A' for option A or 'B' for option B.");
      String input = keyboard.next();
      input.toLowerCase();
      input.charAt(0);  
    }
    while ((input != "a") || (input != "b"));
}

输入字符串总是出现重复的局部变量错误.

I always get a Duplicate Local Variable error with the input String.

任何帮助将不胜感激！

推荐答案

替换

String input = keyboard.next();

与

input = keyboard.next();

如果你在变量名之前放置一个String，它就是一个声明.而且你只能在一个范围内声明一个变量名.

If you put a String before the variable name it is a declaration. And you can declare a variable name only once in a scope.

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