Thread: Java Program: Falling Distance Problem

Here's the explanation of the problem:

PROBLEM:

When an object is falling because of gravity, the following formula can be used to determine the distance the object falls in a specific time period:

d = 1/2gt²

The variables in the formula are as follows:
-"d" is the distance in meters
-"g" is 9.8
-"t" is the amount of time (in seconds) that the object has been falling

Write a method named fallingDistance that accepts an object's falling time (in seconds) as an argument. The method should return the distance (in meters) that the object has fallen during that time interval. Demonstrate the method by calling it in a loop that passes the values 1 through 10 as arguments, and displays the return value.

OTHER STIPULATIONS (Made by Professor):

-Instead of 9.8, make g = 9.80665
-Make "g" a named constant, and declare it locally inside fallingDistance.

And this is the sample Display Output we're suppose to have:

OUTPUT:

output2.png

But, I got this..............

output.png

Lastly, here's my Java program that definitely needs some tweaking:

import java.text.DecimalFormat;
 
public class fallingDistance
{
  public static void main(String[] args)
  {
    int fallingTime = 0;
    String name1 = "Time", name2 = "Distance";
    String name3 = "(seconds)", name4 = "(meters)";
 
    DecimalFormat num = new DecimalFormat("#,###.00");
 
    System.out.println("Falling Distance\n");
    System.out.printf("%s %15s\n", name1, name2);
    System.out.printf("%s %10s\n", name3, name4);
    System.out.println();
 
    for(int i = 1; i <= 10; i++)
    {
       fallingTime++;
       if(fallingTime > 1)
       {
         System.out.println(fallingTime + "           " + num.format(fallingDistance(i)));
       }
    }
  }
 
  public static double fallingDistance(double fallingTime)
  {
    double g = 9.80665, a = 0.5;
    double d = a * g * Math.pow(fallingTime,2);
    return d;
  }
}

I'll fix the spacing, making g constant, and all the little stuff. Just need help with the following:

NEED TO:

1) include the 1 and 4.90. It's not showing up for some reason, and don't know exactly how to put it in there.
2) Get the decimal points lined up.

PLEASE HELP ME! Thanks!

Originally Posted by Mugambbo

One line of your code in your for loop skips the first result and that is: fallingTime++; I'll suggest you use: System.out.printf() to format the distance output, if thats more easier.

All I had to do was include "=" to if(fallingTime > 1).

Here's my updated Java code:

public class fallingDistance
{
  public static void main(String[] args)
  {
    int fallingTime = 0;
    double results;
    String name1 = "Time", name2 = "Distance";
    String name3 = "(seconds)", name4 = "(meters)";
    results = distance(fallingTime);
 
    System.out.println("Falling Distance\n");
    System.out.printf("%s %15s\n", name1, name2);
    System.out.printf("%s %10s\n", name3, name4);
    System.out.println();
 
    for(int i = 1; i <= 10; i++)
    {
       fallingTime++;
       if(fallingTime >= 1)
       {
         System.out.println(" " + fallingTime + "           " + results);
       }
    }
  }
 
  public static double distance(double fallingNum)
  {
    final double g = 9.80665;
    double a = 0.5, d;
    d = a * g * Math.pow(fallingNum,2);
    return d;
  }
}

Now, I'm getting this since I'm trying to use the Printf Method:

javaDistanceFalling.png

When I should be getting this as my output:

output2.png

Originally Posted by Norm

If you want the value of results to change every time it is printed, the code needs to assign it a new value.
Otherwise its value won't change and the loop will print the same value every time.
Move the assignment statement inside the loop so result is changed every time the loop goes around.

I was able to get the value of seconds to change (e.g. 1, 2, 3, 4, 5...10). How do I get the value to change for meters is the question I'm asking.

Okay, I'm getting somewhere now. Here's what I have

javaDistanceFalling.png

And just need to get it to look like this:

output2.png

I know the whole printf method to align everything, but I can't seem to get this part of the code to work:

for(int i = 1; i <= 10; i++)
    {
       fallingTime++;
       if(fallingTime >= 1)
       {
         System.out.println(fallingTime + "          " + distance(i));
         //  System.out.printf("%2.0f %20.2f\n", fallingTime, distance(i));
       }
    }

The printf method you see is not letting me compile correctly. Any advice/input?

Originally Posted by Norm

Can you copy and paste the message? Not post an image.

Falling Distance

Time Distance
(seconds) (meters)

Exception in thread "main" java.util.IllegalFormatConversionException: f != java.lang.Integer
at java.util.Formatter$FormatSpecifier.failConversion (Formatter.java:4045)
at java.util.Formatter$FormatSpecifier.printFloat(For matter.java:2761)
at java.util.Formatter$FormatSpecifier.print(Formatte r.java:2708)
at java.util.Formatter.format(Formatter.java:2488)
at java.io.PrintStream.format(PrintStream.java:970)
at java.io.PrintStream.printf(PrintStream.java:871)
at fallingDistance.main(fallingDistance.java:22)

Originally Posted by Norm

That is not a compiler error. It happens when the code is executed.
Did you look up the error message?
Also read the API doc for the format control characters. The error message says that the letter f is NOT for integers.

Don't have time to look up for these errors, but--anyways--I actually figured it out. Thanks, I suppose.