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Thread: Rounding with printf

  1. #1
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    Default Rounding with printf

    Hello, I made a program and it works great, but I need the height to be rounded to the nearest 0.1

    Here is the program:
    import java.util.Scanner;
     
    public class BouncingBall
    {
      public static void main(String[] args)
      {
        Scanner keyboard = new Scanner(System.in);
        int bounce = 0, time = 0;
        double height = 0.0;
        double velocity = 0;
     
        System.out.println("Enter the initial velocity of the ball: ");
        velocity = keyboard.nextDouble();
     
        do
        {
          System.out.println("Time: " + time + " Height: " + height);
          time ++;
     
          height += velocity;
          velocity -= 32;
     
          if (height < 0)
          {
            height *= -0.5;
            velocity *= -0.5;
            bounce++;
     
            System.out.println("Bounce!");
          }
        } while (bounce < 5);
      }
    }

    I tried System.out.printf("Time: " + time + " Height: " + height); instead of println, but the output looks all funny. However, all the numbers are rounded properly. How do I make it so the output doesn't get all messed up?


  2. #2
    Super Moderator jps's Avatar
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    Default Re: Rounding with printf

    What do you mean by "looks all funny" and "get all messed up"
    If you search printf you should find plenty of samples as well as documentation to show how to use it.
    If you run into a problem you can not solve show the code with the printf statement and explain what the problem is

  3. #3
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    Default Re: Rounding with printf

    Sorry I wasn't more specific.

    Here's how the output looks when I use println:
    Time: 0 Height: 0.0
    Time: 1 Height: 100.0
    Time: 2 Height: 168.0
    Time: 3 Height: 204.0
    Time: 4 Height: 208.0
    ...
    Here's how the output looks when I use printf:
    Time: 0 Height: 0.0Time: 1 Height: 100.0Time: 2 Height: 168.0Time: 3 Height: 204.0Time: 4 Height: 208.0 ...
    Each time and height is outputted onto the same line (which I don't want), but the height values are rounded to the tenth value in later values (which is what I do want).

  4. #4
    Member Kewish's Avatar
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    Default Re: Rounding with printf

    Do you know what the ln stands for in println?
    Look for an equivalent in Formatter API

    Look under conversions header in that doc. It may not be clear straight away, but you will want to escape that character.

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