Java 错误：在声明变量之前找不到符号？
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Java Error: cannot find symbol yet the variables are declared?
提问by Reddy
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");
}
}
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.
嘿伙计们，我正在尝试使用 Java 制作一个简单的程序，以找出以军用时间给出的 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，它都会给我一个关于变量小时和最后打印行中变量分钟的错误，说“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。
回答by Karthik T
When you define a object reference or any primitive variable inside a ifblock (or any such block), it is accessible only within that block.
当您在if块（或任何此类块）内定义对象引用或任何原始变量时，它只能在该块内访问。
Change as below
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);
}
回答by Sean F
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.
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");
}
}
so you can initialise them to "" or to remove unnecessary else statement initialise them to the else valuse
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 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");
