Using a Markov Model to analyze a text input in Java

Question

I'm very new to Java and I'm required to use a Markov Model to analyze a text (String) input. I will be honest: this is for an assignment. I am looking to learn how to answer it, not just copy and paste code.

The code I am working with (this is given and cannot be altered) is below:

public class MarkovModel
{

    /** Markov model order parameter */
    int k; 
    /** ngram model of order k */
    NgramAnalyser ngram; 
    /** ngram model of order k+1 */
    NgramAnalyser n1gram; 

    /**
     * Construct an order-k Markov model from string s
     * @param k int order of the Markov model
     * @param s String input to be modelled
     */
    public MarkovModel(int k, String s) 
    {
        //TODO replace this line with your code
    }

the exact question is: Complete the code for the constructor, which takes an integer k, and an input string s, and initializes any data structures needed for a k-th order Markov model.

We are also using an n-gram analyser, and the text should wrap around (for example, with "abbbc", the 3-grams would be abb, bbb, bbc, bca, and cab). Please let me know if you need any more information! Again, I am not looking to copy and paste code, just want a little bit of help understanding how to solve it.

Thanks in advance.