Java help! Do while boolean is false loop?

I want to program to keep asking for user inputs, until they input a number. But this - if the first input number is not a number, it will infinitely print the output statement, not allowing the user to type a new line.
Boolean good = true;
System.out.println("Input base number (floating point):");
if (keyboard.hasNextDouble())
a = keyboard.nextDouble();
else
do
{
System.out.println("Input base number (floating point):"); //must be numbers.
a = keyboard.nextDouble();
if (keyboard.hasNextDouble())
{
a = keyboard.nextDouble();
break;
}
else
good = false;
}while (!good)

import java.util.Scanner;
public class ans1
{

public static void main (String [] args)
{
Boolean good = false;

Scanner keyboard = new Scanner(System.in);

Double a;
String b;
System.out.println("Input base number (floating point):"); //asking for your input

good=false; //keep good=false to tell the computer that there is no valid input
while (!keyboard.hasNextDouble()) // if no number is entered then keep asking for it
{
if (!good) //this if statement is here to ask for the input
{
good=true;
System.out.println("Input base number (floating point):"); //<----------------------
// |
} // |
// |
if (keyboard.hasNextDouble()) //if it is a number then assign the value to ur variable |
a = keyboard.nextDouble(); // ...
else // |
good=false; //tell the computer to output the message again --------------------


b = keyboard.next(); //dumby input to wait for a value

}



}
}

I think you error is this:

You declare good as true in the beginning, so if your first input is not a number it is changed to false but nowhere in the while loop do you turn it back to true, so the while loop will never end.

What you should do is this:

if (keyboard.hasNextDouble())
{
a = keyboard.nextDouble();
good = true;
}

That should solve your problem... I think =)

Good luck

Here's a solution, but try to either get yours to work or understand my solution by stepping through it with a debugger.

package com.kaydell.answers;

import java.util.Scanner;

public class ReadData {

// The method readDouble was made to be generally useful.

public static double readDouble(Scanner in) {
double d = 0.0;
boolean good = false;
do {
System.out.println("Input a decimal number: \n");
String input = in.next();
try {
d = Double.parseDouble(input);
good = true;
} catch (Exception e) {
good = false;
}
System.out.println("You entered the input'" + input + "'");
if (!good) {
System.out.println("The string: '" + input + "' is not a valid decimal number. Try again.");
}
} while (!good);
return d;
}

// this main method is just to test the readDouble() method.

public static void main(String[] args) {
Scanner keyboard = new Scanner(System.in);
double d = readDouble(keyboard);
System.out.println("You entered the decimal number: " + d);
}


}