Checks if two strings are isomorphic i.e if the characters in source can be replaced to transform into target. The oder should be preserved. Characters can map to themselves but two different characters cannot map to the same character.Checks if two strings are isomorphic i.e if the characters in source can be replaced to transform into target. …

Isomorphism.java

import java.util.HashMap;

public class Isomorphism {
  /**
  * Checks if two strings are isomorphic
  */
	public static boolean isIsomorphic(String source, String target) {

		if (source == null || target == null)
			return false;
		if (source.length() != target.length())
			return false;
		HashMap<Character, Character> transformationMap = new HashMap<Character, Character>();
		for (int i = 0; i < source.length(); i++) {

			char sch = source.charAt(i);
			char tch = target.charAt(i);

			if (transformationMap.containsKey(sch)) {
				char val = transformationMap.get(sch);
				if (val != tch)
					return false;
			} else {

				if (!transformationMap.containsValue(tch))
					transformationMap.put(sch, tch);
				else
					return false;
			}

		}
		return true;

	}

	public static void main(String[] args) {
		System.out.println(isIsomorphic("egg", "add"));
	}

}