Help with Random Number Generator

[celtics]

Hey guys

I need to make a program that is a guessing game. The user enters a number from 1 to 20 and my program tries to guess it using its previous guesses as parameters in a random number generator. The problem I'm having is how to generate a random number from the first guess to the number 20 (look at my firstGuessLow method) and how to generate a random number from the lowest possible guess to the highest possible guess (look at my secondGuess method).

import java.util.Scanner;
import java.util.Random;

public class GuessingGame {

	Scanner keyboardReader = new Scanner(System.in);
	Random numberGenerator = new Random();
	int number, userNumber, highNum, lowNum, minMaxNum;
	String input;

	
	public GuessingGame(Scanner input)
	{
		keyboardReader = input;
		number = numberGenerator.nextInt();	

	}
	public void StartGame()
	{
		/* Print an invitation to the user to think
		*  of a number from 1 to 20
		*/
		System.out.println("Type a number from 1 to 20");
		userNumber = keyboardReader.nextInt();
		
		// Give the user the first guess and store it in number
		System.out.println("I will try to guess your number.");
		number = numberGenerator.nextInt(20) + 1;
		
		// Consume the remaining newline
		keyboardReader.nextLine();
		
		System.out.println("My guess is " + number + ". Is this number high, low, or correct?");
		input = keyboardReader.nextLine();
		
		if (input.equals("high")){
			firstGuessHigh(number);
		}
		else if (input.equals("low")){
			firstGuessLow(number);
		}
		else if (input.equals("correct"))
		{
			System.out.println("I win!");
		}
	}
	public void firstGuessHigh (int highestValue)
	{
		/* 
		 * Generate a random number from 1 to highestValue
		 */
		highNum = numberGenerator.nextInt(highestValue) - 1;
		
		System.out.println("My second guess is " + highNum + ". Is this number high, low, or correct?");
		input = keyboardReader.nextLine();
		if (input.equals("high")){
			secondGuess(1, highNum);
		}
		else if (input.equals("low")){
			secondGuess(highNum, number);
		}
		else if (input.equals("correct"))
		{
			System.out.println("I win! It only took me two tries!");
		}
		
	}
	public void firstGuessLow (int lowestPossible)
	{
		/*
		 * Generate a random number from lowestPossible to 20
		 */
		
		lowNum = numberGenerator.nextInt(lowestPossible) + lowestPossible + 1;
		System.out.println("My second guess is " + lowNum + ". Is this number high, low, or correct?");
		input = keyboardReader.nextLine();
		if (input.equals("high")){
			secondGuess(number, lowNum);
		}
		else if (input.equals("low")){
			secondGuess(lowNum, 20);
		}
		else if (input.equals("correct"))
		{
			System.out.println("I win! It only took me two tries!");
		}
	}
	public void secondGuess (int minGuess, int maxGuess)
	{
		// Generate a random number from minGuess to maxGuess
		minMaxNum = numberGenerator.nextInt(maxGuess) + minGuess;
				
		System.out.println("My final guess is " + minMaxNum + ". Is this number correct?(Please type yes or no)");
		input = keyboardReader.nextLine();
		if (input.equals("yes")){
			System.out.println("I win! It only took me three tries!");
		}
		else if (input.equals("no")){
			System.out.println("You win! Congratulations!");
		}
	}
}