Pergunta de entrevista da empresa Akamai

reverse of a string. || method overriding.|| Given a string s1="ABCDEF"; S2 ="123456"; S3="12ABCD34E5F6" is valid string that is S3 should have all the all characters from both S1 and S2 . The order in which they appear in S3 should be the same order in the respectively string S1 and S2 ||. Rules to override a method in java sub-class. Java collection like hashmap,hashtree, linkedlist ..etc .