Java错误：找不到符号但是声明了变量？

问题描述

import java.util.Scanner;
public class Assignment1Q3
{
    public static void main(String[] args)
    {
    Scanner in = new Scanner(System.in);
    System.out.print("Please enter the first time: ");
    int fTime = in.nextInt();
    System.out.print("Please enter second time: ");
    int lTime = in.nextInt();
    int tDifference = Math.abs(fTime - lTime);
    String strTDiff = String.valueOf(tDifference);
    int length = strTDiff.length();
    if (length == 4)
    {
        String hours = strTDiff.substring(0, 2);
        String minutes = strTDiff.substring(3, 5);
    }
    else if (length == 3)
    {
        String hours = strTDiff.substring(0);
        String minutes = strTDiff.substring(2, 4);
    }
    else
    {
        String hours = ("0");
        String minutes = strTDiff.substring(0, 1);
    }
    System.out.println(hours + " hours " + minutes + " minutes");
    }
}

嘿大家好我试图用一个简单的程序Java查找军事时间给出的2次之间的差异，并以小时和分钟的数量给出输出。每当我在命令提示符下编译它时，它会给出一个变量小时的错误，以及上一个打印行中的变量分钟无法找到符号。我想在if语句之前尝试声明它们，但这也不起作用。我很抱歉，但我对编程很感兴趣并感谢所提供的任何帮助。

Hey guys so im attempting to make a simple program using Java to find the difference between 2 times given in military time and to give the output in number of hours and minutes. Whenever i compile this in command prompt it gives me an error for the variable hours and the variable minutes in the last printing line saying "cannot find symbol". I thought trying to declare them before the if statement but that did not work either. I apologize but i am very new to programming and appreciate any help offered.

推荐答案

通过在if语句中调用String，它们只存在在if语句中，你需要在if语句之外对它们进行十进制并将其与if中的值相关联。

By calling String within the if statements they only exist within the if statement you need to decalre them outside of the if and associate a value within the if.

import java.util.Scanner;
public class Assignment1Q3
{
    public static void main(String[] args)
    {
    Scanner in = new Scanner(System.in);
    System.out.print("Please enter the first time: ");
    int fTime = in.nextInt();
    System.out.print("Please enter second time: ");
    int lTime = in.nextInt();
    int tDifference = Math.abs(fTime - lTime);
    String strTDiff = String.valueOf(tDifference);
    int length = strTDiff.length();
    String hours = "";
    String minutes = "";

    if (length == 4)
    {
        hours = strTDiff.substring(0, 2);
        minutes = strTDiff.substring(3, 5);
    }
    else if (length == 3)
    {
        hours = strTDiff.substring(0);
        minutes = strTDiff.substring(2, 4);
    }
    else
    {
        hours = ("0");
        minutes = strTDiff.substring(0, 1);
    }
    System.out.println(hours + " hours " + minutes + " minutes");
    }
}

因此您可以将它们初始化为或删除不必要的else语句将它们初始化为else valuse

so you can initialise them to "" or to remove unnecessary else statement initialise them to the else valuse

    String hours = "0";
    String minutes = strTDiff.substring(0, 1);

    if (length == 4)
    {
        hours = strTDiff.substring(0, 2);
        minutes = strTDiff.substring(3, 5);
    }
    else if (length == 3)
    {
        hours = strTDiff.substring(0);
        minutes = strTDiff.substring(2, 4);
    }
System.out.println(hours + " hours " + minutes + " minutes");

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