GlobalLogic Senior Software interview questions

Write a Student class, make list and put student objects in that and then sort it on basis of name Overide hashCode(), equals() method for Student class Write a program to show ConcurrentModificationException and how to overcome this Write Sigleton class. Will this also work in case of Serialization, Reflection Fail-Fast and Fail-safe? Iterator is fail fast or fail safe? What is aggregation? What will happen if hashCode return constant value in all case? How TreeSet works?