Nasdaq interview questions

JAVA Q. what are the reules of overriding. Why the rules are like that? I can understand if some one asked me why we cannot override static methodds. Q: List 5 demariies of ReactJS. Q: Leet code. A list contains many Strings except one string other can apper any number of times(duplicate strings Q: In transaction, while one thread will do updation another thread can not access it , dont use synchronization.