Java Interview Questions - NTT DATA


Below questions asked in NTT DATA telephonic interview - JAVA 4 years exp:
  1. How to make a class as immutable ? 
  2. Why String class is immutable ?
  3. What is the difference between abstract class and interface ?
  4. When to use abstract class and interface ?
  5. What is the difference between collections.synchronizedmap and concurrenthashmap ?
  6. What is the countdownlatch and cyclicbarrier ?
  7. What is the difference between wait() and sleep()?
  8. What happens if an object is serializable but it includes a reference to a non-serializable object?
  9. What is synchronization ?
  10. What is SQL injection ?
  11. How HashMap works internally?
Location: Hyderabad, Telangana, India

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