Iris Software Java Technical Lead interview questions

Overall exp., technologies worked upon, versions, duration Hashcode vs equals, contract b/w both by java Save employee object in hashmap when hashcode returns 1 and equals always “true” , and make e1,e2,e3 as key or employee.id as key, size of hashmap will be? Method overriding Class lock, method lock Can we take lock on object of class when class level lock is already acquired Executer apis in java How to restrict add method on list Diff scopes in spring Are controllers threadsafe How to make the same threadsafe Runnable vs callable Aggregation and composition Hibernate caching Session vs session factory Comparable vs comparator

Q1. What is java memory model explain it? Q2. How Hashmap works internally many questions on the hashmap working. a. What is the data structure is used to store entity? b. how hashcode works with the performace of hashmap? c. What is the good way to override hashmap? d. Which version of java uses Red Black tree for storing hash entity having hashcode collision? e. What is hash collision explain that. write some code which uses a class as key and override hashcode and equals mehod in that. f.write code for good hashcode. Q3 What is Executor framework in java? a. write code for creating threads using executor framework. b. How will you assign threads doing subtask in executor framework? c. What is Lock? d. which is concurrency package, what are the classes in that? e. what is semaphore? Where it is used? f.Tell something about producer and consumer problem, which class of queue interface is used to solve it? Q4 How ArrayList works? which Collection is resizable? when arraylist grows what is the new size?