长时间存储百分比的问题

Question

I am trying to write a program for class that reads a list of hours worked annually from a .txt file, assigns/reads (A little fuzzy on the proper terminology :)) them into an array, and then calculates overages and prints them.

When I run, console output is as follows:

Employee 1 worked 1600 hours, an under-run of 160 or 0%
Employee 3 worked 1680 hours, an under-run of 80 or 0%

Why are the percentages zero?

import java.io.*;
import javax.swing.*;

class Calculator 
{
 public static void main(String args[])
  {

  try{

      String filePathString=JOptionPane.showInputDialog(null,"What is the file path?");  

      FileInputStream fstream = new FileInputStream("C:\\hello.txt");
      BufferedReader br = new BufferedReader(new InputStreamReader(fstream));
      String strLine;
      int counter = 0;
      long[] Array = new long[5];   


      //Read File Line By Line
      while (counter <= 4)

        {
            strLine = br.readLine();
            Array[counter] = Long.parseLong(strLine); 
            OverageUnderage(Array[counter], counter);
            counter = counter + 1;
        }

  //Close the input stream
  in.close();

    }

  catch (Exception e){//Catch exception if any
  System.err.println("Error: " + e.getMessage());
  }
  }

 public static long OverageUnderage(long hours, long counter)
 {
 long overageAmount = 0;
 long overagePercent = 0;

     if (hours < 1760)
     {    
        overageAmount = 1760 - hours;
        overagePercent = ((overageAmount/1760)*100);

        System.out.println("Employee "+counter+" worked "+hours+" hours, an under-run of "+overageAmount+" or "+overagePercent+"%");
    }

    return counter;
 }

}

Answer 1

The number ( overageAmount / 1760 ) is being treated as a long, not a double, which you'll need. Try:

overagePercent = ( ( overageAmount / 1760.0 ) * 100 );

using the .0 on 1760 will have it treated as a decmial value. This will prevent the rounding to 0 issue you were seeing, and allow the calculation to have decimals for the rest of the calculations, providing you with your desired result.

Answer 2

That's why (IMHO) you divide long instead of doubles:

overagePercent = ((overageAmount / 1760)*100);

Here overageAmount/1760 returns 0 !
So you have two solutions:

1. First convert overageAmount to double and then execute the operation
2. Divide with float 1760.0 so resulting number is already a float

Answer 3

The order you perform the calculations matters, especially for int values.

Instead of

overagePercent = overageAmount / 1760 * 100;

which is likely to be 0 * 100 or 0 you can do

overagePercent = overageAmount * 100 / 1760;

this could still be 0, but only if the answer is less than 1.

Answer 4

If you need to get answer in decimals, you have to use double or decimal. You cant use Long which is for integers.