UKG Java Web Applications Developer interview questions

2 Round (Virtual)- They asked to write function to add, reverse, print and sort the linkedlist. They asked about ManyToMany mapping and implementation(create Book, Author class). The asked to write a query where there's book and author table and another table Book_Author.. now write a query to fetch all the book name by whose authore.gender == "FEMALE". 3 Round (F2F) - String s1 = new String("xyz"); String s2 = "xyz"; Map m = new HashMap(); m.put(s1,1); m.put(s2,2); m.length ???? - 1 why? ---------------------------------- class Employee{ id, name } Map h1 = new HashMap(); Can we have Employee as key here? How? what change we need to do in Employee class? and what will happen if i have 2 same id,name have? ans - hashable(), equals() method.. -------------- How can i sort the map by Employee id ? - Comparator vs Comparable -- Implementation ------------- Threads... Thread pool.. Executive Framework... ------------- if I have 5 threads and all of it have task... there's another task come up how will and which thread will be assigned ? ------------- Internal working of volatile keyword? How does it internally work? ------------------------------------------- Clustered vs Non Clustered Index in sql, postgresSQl -------------------------------------------- What is the most challenging thing have you done in your job?