Minimum Window Riddle

package riddles.strings;

import java.util.Arrays;
import java.util.HashSet;
import java.util.TreeMap;
import java.util.TreeSet;

public class MinimumWindow {

    public static WindowObject getMinWin(char[] s, char[] c){

        WindowObject minWindow = null;

        /* Creating HashSet in order to query the chars in O(1) */
        HashSet<Character> dic = new HashSet<Character>();
        for(int i = 0; i < c.length; i++){
            dic.add(c[i]);
        }

        /* In order to keep track of "where I've seen it" */
        TreeMap<Character, Integer> where = new TreeMap<Character, Integer>();
        /* In order to keep the indexes sorted */
        TreeSet<Integer> indexInWindow = new TreeSet<Integer>();

        for(int i = 0; i < s.length; i++){
            if(dic.contains(s[i])){
                /* If I've already seen this char */
                if(where.containsKey(s[i])){
                    /* Remove its old index */
                    indexInWindow.remove(where.get(s[i]));
                }
                /* Update/Insert its index */
                where.put(s[i], i);
                indexInWindow.add(i);

                if(indexInWindow.size() == dic.size()){ /* I've seen all of them*/
                    /* These are the window's edges */
                    int firstIndex = indexInWindow.first();
                    int lastIndex = indexInWindow.last();
                    WindowObject currentWindow = new WindowObject(s, firstIndex, lastIndex);
                    if(minWindow == null){ /* It's the first windows I see */
                        minWindow = currentWindow;
                    }else{
                        if(minWindow.compareTo(currentWindow) > 0){
                            /* If the minWindow bigger than what I just found */
                            minWindow = currentWindow;
                        }

                    }

                }

            }
        }

        return minWindow;
    }

    public static void main(String args[]){
        String s = "ADOBECODEBANC";
        String c = "ABC";
        WindowObject wo = MinimumWindow.getMinWin(s.toCharArray(), c.toCharArray());
        if(wo == null){
            System.out.println("Sorry! No windows were found!");
        }else{
            System.out.println("Found a Min Window with lenght: ["+wo.getWindow().length+"]");
            System.out.println("Here it is: "+wo);
        }
    }

    static class WindowObject implements Comparable<WindowObject>{
        private char[] window;
        private int firstIndex, lastIndex;

        public WindowObject(char[] s, int firstIndex, int lastIndex){
            this.window = Arrays.copyOfRange(s, firstIndex, lastIndex+1);
            this.firstIndex = firstIndex;
            this.lastIndex = lastIndex;
        }

        public char[] getWindow(){
            return this.window;
        }

        @Override
        public int compareTo(WindowObject w) {
            if(this.window.length < w.getWindow().length){
                return -1;
            }
            if(this.window.length > w.getWindow().length){
                return 1;
            }
            return 0;
        }

        @Override
        public int hashCode(){
            return this.window.hashCode();
        }

        @Override
        public boolean equals(Object o){
            if(!(o instanceof WindowObject)){
                return false;
            }
            WindowObject w = (WindowObject) o;
            return this.window.length == w.getWindow().length;
        }

        @Override
        public String toString(){
            String s = "";
            for(int i = 0; i < this.window.length; i++){
                s += this.window[i];
            }
            return s+" ["+this.firstIndex+"]["+this.lastIndex+"]";
        }

    }

}