Java Program To Check Isomorphic Strings

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import java.util.HashMap;
import java.util.Map;

public class JavaIsomorphicStrings {

	public static void main(String[] args) {
		checkIfIsoMorphic("paper", "title");
		checkIfIsoMorphic("foo", "app");
		checkIfIsoMorphic("foo", "bar");
		checkIfIsoMorphic("turtle", "tletur");
		checkIfIsoMorphic("add", "egg");
		checkIfIsoMorphic("br", "rr");
	}

	private static void checkIfIsoMorphic(String s1, String s2) {
		if (s1.length() == s2.length()) {
			s1 = s1.toLowerCase();
			s2 = s2.toLowerCase();
			if (s1.equals(s2)) {
				System.out.println(s1 + " and " + s2 + " are Isomorphic");
			} else {
				boolean isomorphic = true;
				Map<Character, Character> map = new HashMap<Character, Character>(0);
				for (int i = 0; i < s1.length(); i++) {
					char c1 = s1.charAt(i);
					char c2 = s2.charAt(i);
					if (map.containsKey(c1)) {
						if (map.get(c1) != c2) {
							isomorphic = false;
							break;
						}
					} else {
						if (map.containsValue(c2)) {

							isomorphic = false;
							break;
						} else {
							map.put(c1, c2);
						}
					}
				}
				if (isomorphic) {
					System.out.println(s1 + " and " + s2 + " are Isomorphic");
				} else {
					System.out.println(s1 + " and " + s2 + " are not Isomorphic");
				}
			}
		} else {
			System.out.println(s1 + " and " + s2 + " are not Isomorphic");
		}
	}
}
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