Thread: help me with a conversion program please

okay so everything compiles BUT i have been stuck on why it doesnt work for days. When I compile it says " ----jGRASP: process aborted by user.

----jGRASP exec: java Conversion
Wht am I doing wrong?

import java.util.Scanner;
import java.text.DecimalFormat;
 
public class Conversion
{
	DecimalFormat formatter = new DecimalFormat("##0.0000");
 
	public static void main(String[]args)
 
	{
 
	showMenu();
 
	}
	public static void showMenu()
	{
 
		double meters = 0.0;
		Scanner keyboard = new Scanner(System.in);
		do 
		{
		meters = keyboard.nextDouble();
 
 
 
		if (meters<0)
		System.out.println("Please enter a positive number");
		meters=keyboard.nextDouble();
		} 
		while (meters>0);
		menu(meters);
	}
 
	 public static void menu(double meters)
	{
		int selection=0;
		Scanner keyboard = new Scanner(System.in);
 
 
		while(selection !=4)
		{
 
		System.out.println("METER CONVERSION");
		System.out.println("1) Convert to Kilometers");
		System.out.println("2) Convert to Inches");
		System.out.println("3) Convert to Feet");
		System.out.println("4) Quit the Program");
		System.out.println("Please make a selection:");
		selection = keyboard.nextInt();
 
 
			switch(selection)
			{
 
			case 1 :
			showKilometers(meters);
			System.out.println("Please enter the number of meters you want to convert:");
			meters=keyboard.nextDouble();
			break;
 
			case 2:
 
			showInches(meters);
			System.out.println("Please enter the number of meters you want to convert:");
			meters=keyboard.nextDouble();
			break;
 
 
			case 3:
			showFeet(meters);
			System.out.println("Please enter the number of meters you want to convert:");
			meters=keyboard.nextDouble();
			break;
 
			case 4:
			System.out.println();
			break;
 
 
			default:
			System.out.println("Invalid selection.");
			System.out.println();
 
			}
		}
	}
 
 
	public static double showKilometers(double meters)
	{
	double kilometers = 0.0;
	kilometers = meters * 0.001;
 
	System.out.println(meters+ " meters is " + kilometers + " kilometers.");
	return kilometers;
	}
	public static double showInches(double meters)
	{
	double inches = 0.0;
	inches=meters * 39.37;
 
	System.out.println(meters + " meters is " + inches + " inches.");
	return inches;
	}
	public static double showFeet(double meters)
	{
	double feet = 0.0;
	feet=meters * 3.281;
 
	System.out.println(meters + " meters is " + feet + " feet.");
	return feet;
	}
}

Well my program has to run like this over and over till the user quits the program
METER CONVERSION
1) Convert to Kilometers
2) Convert to Inches
3) Convert to Feet
4) Quit the Program
Please make a selection:
Invalid selection.

METER CONVERSION
1) Convert to Kilometers
2) Convert to Inches
3) Convert to Feet
4) Quit the Program
Please make a selection:
Please enter the number of meters you want to convert:
Invalid entry.
Please enter a positive number:
Invalid entry.
Please enter a positive number:
Invalid entry.
Please enter a positive number:
125.0 meters is 0.1250 kilometers.


but it doesnt run and shows this
METER CONVERSION
1) Convert to Kilometers
2) Convert to Inches
3) Convert to Feet
4) Quit the Program
Please make a selection:
Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Scanner.java:838)
at java.util.Scanner.next(Scanner.java:1461)
at java.util.Scanner.nextInt(Scanner.java:2091)
at java.util.Scanner.nextInt(Scanner.java:2050)
at Conversion.menu(Conversion.java:55)
at Conversion.showMenu(Conversion.java:37)
at Conversion.main(Conversion.java:18)

I been trying to see the error in this code for so long but can't seem to figure out what I'm doing wrong :/