implementing another class to create the first 100 prime numbers

ok I'm a little mind blown from an assignment i have to do. We have to implement a sequence class from http://ift.tt/25vn9fB (the chapter 10 example) to make a new class called PrimeSequence and it has to right align the first 100 prime sequence numbers. I don't understand the point of implementing the other class and i did it but i know im not following the assignment rules because i dont understand what im supposed to implement from the other class and i also use nothing from the other class. I'm not sure on what i have to do

Sequence Class

public interface Sequence 
{   
    int next();
}

PrimeSequence Class

public class PrimeSequence implements Sequence
{

public PrimeSequence()
{

}

public boolean isPrime(int x)
{
    for (int start = 2; start <= Math.sqrt(x); start++)
    {
        if (x % start == 0) 
        {
            return false;
        }
    }
    return true;
}

    public int next()
    {

    }
}

PrimeSequenceTester

public class PrimeSequenceTester {


public static void main(String[] args) 
{
    PrimeSequence prime = new PrimeSequence();

    int currentNumber = 2;
    int primesFound = 0;

    while (primesFound < 100) {
        if (prime.isPrime(currentNumber)) 
        {
            primesFound++;

            System.out.printf("%4s",currentNumber + " ");
            if (primesFound % 10 == 0) 
            {
                System.out.println();
            }
        }

        currentNumber++;
}
}