重复局部变量（For循环） [英] Duplicate local variable(For Loops)

问题描述

我正在尝试解决一个任务（我还对Java非常新），并且通过许多资源来梳理这个冲突，但仍然无法完全实现（注意：金枪鱼是我的Scanner变量）

I'm trying to solve 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.(NOTE: Tuna is my Scanner variable)

    int counted, sum, counted1;


    System.out.print("Enter your number to be calculated: ");
    counted = tuna.nextInt();
    counted1 =tuna.nextInt();


    for(int counted=0;counted<=counted1;counted++){
        System.out.println("The sum is: "+ counted);
    }
}

}

结果是：
线程main中的异常java.lang.Error：未解决的编译问题：
计算重复的局部变量

Result is: Exception in thread "main" java.lang.Error: Unresolved compilation problem: Duplicate local variable counted

我应该解决的问题是：

编写一个程序以读取数字，并将所有数字从1到该数字相加。例如，如果
是6的用户密钥，则输出为21（1 + 2 + 3 + 4 + 5 + 6）。

Write a program to read in a number and sum up all the numbers from 1 to that number. For e.g, if the user key in 6, then the output is 21 (1+2+3+4+5+6).

添加：我读了一个很相似的问题（），但是我没有通过以前声明这个错误。

ADDED: I read a question() that is rather similar but I did not make the smae mistake by declaring it before.

推荐答案

在相同范围内声明具有相同名称的两个变量：计数被声明在循环之外和循环内。顺便说一句，根据你的规范：

You are declaring two variables with the same name in the same scope: counted is declared outside the loop and inside the loop. By the way, according to your specification:

写一个程序读入一个数字，并将所有的数字从1到这个数字相加。例如，如果用户键入6，则输出为21（1 + 2 + 3 + 4 + 5 + 6）

因为它是一个常数（常数1），所以需要第一个计数 var。你可以这样声明1为常数：

you don't need the first counted var, because it is a constant (the constant 1). You can, so, declare 1 as a constant this way:

final int STARTING_NUMBER = 1

然后在循环中使用此常量：

and then use this constant in your loop:

int counted, sum;
counted = tuna.nextInt();    

for(int index=STARTING_NUMBER;index<=counted;index++){
    sum=sum+index;
}
System.out.println("The sum is: "+ sum);

编辑：可以随时声明变量。重要的是你在同一个范围内宣告他们一次。您可以执行以下操作：

you can declare your variables wherever you want. The important is that you declare them once in the same scope. You can do something like:

int counted, sum, index;
counted = tuna.nextInt();    

for(index=STARTING_NUMBER;index<=counted;index++){
    sum=sum+index;
}
System.out.println("The sum is: "+ sum);

在循环之外声明 index 结果不会改变。但是，声明 for循环用作索引的变量（您可以调用此变量 index 或计数器或 i 或 mySisterIsCool 等）在for循环本身（在其保护下，更精确），以获得更好的可读性。

declaring index outside the loop. The result won't change. It is a common pratice, though, to declare the variable that the for loop uses as index (you can call this variable index or counter or i or mySisterIsCool and so on) inside the for loop itself (in its guard, to be more precise) for a better readability.

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