1 
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");
    }
}

大家好，我正在尝试使用 Java 制作一个简单的程序，以找出军事时间给出的 2 次之间的差异，并以小时数和分钟数给出输出。每当我在命令提示符下编译它时，最后打印行中的变量小时和分钟变量都会出现错误，提示“找不到符号”。我想尝试在 if 语句之前声明它们，但这也不起作用。我很抱歉，但我对编程很陌生，并感谢提供的任何帮助。

4

2 回答 2

2

当您在块（或任何此类块）内定义对象引用或任何原始变量if时，它只能在该块内访问。

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);
}
于 2013-01-30T02:51:49.607 回答
1

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 之外对它们进行 decalre，并在 if 中关联一个值。

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 值

    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");
于 2013-01-30T02:54:44.507 回答