• What do you need to ensure about the object that is a key of a Map.

    public boolean equals(Object o) public int hashCode() // hashCode must be equal for all objects a and b with a.equal(b) == true.

  • Explain synchronized keyword.

  • Java concurrency - how to protect data from concurrent access.

http://www.javaworld.com/article/2078809/java-concurrency/java-concurrency-java-101-the-next-generation-java-concurrency-without-the-pain-part-1.html

  • Explain the use of try, catch, finally.

  • What is the object hierarchy of exceptions.