Question

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");
    }
}

嘿伙计们，我试图用Java编写一个简单的程序来找出军事时间给出的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，它会给我一个变量小时的错误和最后一行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，但我对编程非常陌生，并感谢所提供的任何帮助。

Answer 1

在if块（或任何此类块）中定义对象引用或任何原始变量时，只能在该块中访问它。

更改如下

final String hours, 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);
}

Answer 2

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

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");
    }
}

所以你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

    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");

Java错误：找不到符号但变量是否已声明？

2 个答案: