Cisco interview question

What is hashmap,its internal mechanism, which data structure or Algorithm it uses? What is difference between procidural and object oriented program? Why is no multiple inhiretence not supported in Java even when it's a object oriented program? What are the oops concepts give example of each? What is difference between abstraction and encapsulation? Why is string immutable class? How you can make a immutable class? What is serialisation and what is the use of serialID in it? What is linked list its algorithm and internal working? What is the use of static in Java?