Thread: Java Program - Distance Traveled (Formatting and Decimal Place)

Hi,

I'm having trouble formatting my output and issues with the decimal places. Here's my code:

import java.util.Scanner;
import java.text.DecimalFormat; // Imports DecimalFormat class for one way to round
 
public class lab3
{
  public static void main(String[] args)
  {
    String heading1 = "Hour", heading2  = "Distance Traveled";
    int timeElapsed, hour, speed;
    double distanceTraveled;
 
    Scanner keyboard = new Scanner(System.in);
    DecimalFormat dFormatter = new DecimalFormat("0");
 
    // Ask user for the speed of the vehicle
    System.out.print("What is the speed of the vehicle in mph? ");
    speed = keyboard.nextInt();
 
    while(speed < 0)
    {
      System.out.println("The speed may not be a negative number.");       
      System.out.print("What is the speed of the vehicle in mph? ");        
      speed = keyboard.nextInt();
    }
 
    // Ask user for the number of hours vehicle had traveled
    System.out.print("How many hours has it traveled? ");
    timeElapsed = keyboard.nextInt();
 
    System.out.println();
 
    while(timeElapsed < 1)
    {
      System.out.println("The time must be a positive number.");
      System.out.print("How many hours has it traveled? ");
      timeElapsed = keyboard.nextInt();
    }
 
    // Table displaying the total Distance Traveled
    System.out.printf("%4s %22s\n", heading1, heading2);
    System.out.println();
 
    // Hour initialized
    hour = 0;
 
    for(int i=1; i<=timeElapsed; i++)
    {
      hour++;
      if(hour > 1)
      {
        distanceTraveled = hour * speed;
        System.out.printf("%1d %22f\n", hour, distanceTraveled);
      }
      else
        System.out.println(" " + hour + "                " + speed);
    }
  }
}

And here's my output (Click on the image since it's pretty small):

javaIssues.png

Issue:
1) The Hours 2 and 3 aren't aligned to 1. How do you fix that?
2) The 80 and 120 in Distance Traveled have 6 decimal places when it should not have decimals. How do I fix that?

Feedback is much appreciated!

Okay, I was able to fix Issue #1.

Just had to add some padding to "%d".

Still can't figure out getting rid of the decimal places for the 80 and 120. I have "import java.text.DecimalFormat;" on there, and don't know what to do from there......

Originally Posted by jashburn

There are 2 ways to remove the decimals for issue #2, and they can be done by using just the right formatting in the printf statement.

1. Specify 0 precision

"out" in System.out is a PrintStream object. The API doc for PrintStream.printf is at PrintStream (Java Platform SE 7 ) . You'd see that it refers to Formatter (Java Platform SE 7 ) for the format string syntax.

The general syntax for numeric types is

%[argument_index$][flags][width][.precision]conversion

This means in your case you can specify %22.0f so that the output format will have 0 decimal.

2. Use long type

Your code assumes the speed and time inputs are integers. If you are sticking with this assumption, you can change distanceTravelled from a double to a long. If you do so, you can then use %22d to print out the distance without decimals.

Thanks for the reply.

I just typcasted the double into int (seems to work).

But, can you give me a sample of how your approach will work, too?

Which approach, (1) 0 precision or (2) long type?

Note that for an elementary program it is fine to workaround issues by typecasting. Later on you will want to declare your variables exactly what they should be, and typecast only when really necessary. In your case, consider the result if the multiplication of hour and speed exceeds the upper limit of an int.

Originally Posted by jashburn

Which approach, (1) 0 precision or (2) long type?

Note that for an elementary program it is fine to workaround issues by typecasting. Later on you will want to declare your variables exactly what they should be, and typecast only when really necessary. In your case, consider the result if the multiplication of hour and speed exceeds the upper limit of an int.

#2, I want to know the other way of decimal fomatting. Still a bit confused by it.