is isomorphic

/**
 * Created by mona on 5/26/16.
 */
import java.util.TreeMap;
import java.util.Map;

public class IsomorphicStrings {
    //the words "abca" and "zbxz" are isomorphic
    //aabc a(2) b(1) c(1)
    //create a hashmap sort on value
    //check to see if two hashmap are equal based on their value set
    //assuming two isomorphic strings are of the same length

    public static <Integer, Character> TreeMap reverse(TreeMap<Character,Integer> tmap) {
        TreeMap<Integer,Character> rev = new TreeMap();
        for(Map.Entry<Character,Integer> entry : tmap.entrySet())
            rev.put(entry.getValue(), entry.getKey());
        return rev;
    }

    public static boolean areIsomorphic(String s1, String s2) {
        char[] charArray1 = s1.toCharArray();
        char[] charArray2 = s2.toCharArray();
        TreeMap<Character, Integer> freqMap1 = new TreeMap<>();
        TreeMap<Character, Integer> freqMap2 = new TreeMap<>();
        for (int i=0; i<charArray1.length; i++) {
            if (freqMap1.containsKey(s1.charAt(i))) {
                int freq1 = freqMap1.get(s1.charAt(i));
                freqMap1.put(s1.charAt(i), freq1 + 1);
            }
            else {
                freqMap1.put(s1.charAt(i), 1);
            }

            if (freqMap2.containsKey(s2.charAt(i))) {
                int freq2 = freqMap2.get(s2.charAt(i));
                freqMap1.put(s2.charAt(i), freq2 + 1);
            }
            else {
                freqMap2.put(s2.charAt(i), 1);
            }

        }


        TreeMap<Integer, Character> sortedFreq1= reverse(freqMap1);
        Integer[] freqArr1 = sortedFreq1.keySet().toArray(new Integer[0]);
        TreeMap<Integer, Character> sortedFreq2= reverse(freqMap2);
        Integer[] freqArr2 = sortedFreq2.keySet().toArray(new Integer[0]);
        return freqArr1.equals(freqArr2);

    }

    public static void main(String[] args) {
        String s1="abca";
        String s2="zbxz";
        System.out.println(areIsomorphic(s1, s2));
    }
}