public class Hamming {

    Hamming(String leftStrand, String rightStrand) {
        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
    }

    int getHammingDistance() {
        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
    }

}

@@ -1,11 +1,4 @@
-public 
 clas

change class to package private.