Java Oop

/*    --- Guess what number im thinking for Java. OOP version
    --- E.K.Virtanen 2013, public domain --- */

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

public class GuessOOP{
    // Begin of object Numbers
    public static class Numbers {
        private int randomInteger;
        private int maxRandInteger;

        // Constructor
        public Numbers(int max) {
            maxRandInteger = max;
            randomInteger = randomNumber(maxRandInteger);
        }

        // returns maxRandInteger
        public int returnMax(){
            return maxRandInteger;
        }

        // generates random integer between 1 and maxRandInteger
        public int randomNumber(int maxRandInteger){
            Random randomGenerator = new Random();
            if (maxRandInteger > 0) {
                randomInteger = randomGenerator.nextInt(maxRandInteger) + 1;
            } else {
                randomInteger = 0;
            }
            return randomInteger;
        }

        // checks player guess and returns false/true
        public boolean isCorrect(int guess) {
            if (guess == randomInteger) {
                return true;
            } else {
                return false;
            }
        }

        // returns "lower/higher" depending of player guess
        public String hiLo(int guess) {
            if (guess < randomInteger) {
                return "higher.";
            } else {
                return "lower.";
            }
        }
    } // End of object Numbers

    // method that clears the screen.
    public static void clearScr() {
        for(int i = 0; i < 50; i++) {
            System.out.println();
        }
    }

    public static void main(String[] args) {
        Scanner lukija = new Scanner(System.in);
        Numbers number = new Numbers(100);

        int guess; // player guess
        int counter; // how many 
        counter = 0;

        clearScr();
        System.out.println("Welcome to play \"Guess the number\"");
        System.out.println();
        System.out.println("Cpu just randomed a number between 1 and " + number.returnMax());
        System.out.println("Your job is to guess which number it is.");
        System.out.println("While you play, i give you a tips was your guess too high or low.");
        System.out.println();
        System.out.println("You can exit game by guessing 0 or higher than " +number.returnMax());
        System.out.println();

        do { 
            counter++;
            System.out.println("This is round number: " + counter + ".");
            System.out.print("What is your guess (1 - " + number.returnMax() + "): ");
            guess = lukija.nextInt();

            if (guess > 0 && guess < number.returnMax()) {
                if (number.isCorrect(guess)) {
                    System.out.println("HOORAY!!! You got it!!!");
                    System.out.println("It took " + counter + " rounds.");
                } else {
                    System.out.print("Try " + number.hiLo(guess));
                }    
            }
        } while( number.isCorrect(guess) == false && guess < number.returnMax() && guess > 0);
    }
}