Java interview questions part-1

1. What is singleton class in java ?
Answer :- 

2. what is difference between singleton in java and singleton in spring ?
Answer :-

3. what is immutable in java ?
Answer :-

4. How to create custom immutable class in java ?
Answer :- 

5. Difference between abstraction and encapsulation in java ?
Answer :- 

6. How to achieve abstraction in java ?
Answer :- 

7. How to achieve encapsulation in java ?
Answer :- 

8. What are the 4 basics of OOP ?

Answer :- There four principles of  oop (object-oriented programming) are encapsulation, abstraction, inheritance, and polymorphism.

9. What is solid principle in java ?

Answer :- 
S - Single Responsibility Principle (SRP)
O - Open Closed Principle
L - Liskov Substitution Principle
I - Interface Segregation Principle
D - Dependency Inversion Principle

10. What are the methods in Object class in java ?

11. Enumeration  Vs  Iterator  Vs  ListIterator ?

Enumeration	Iterator	ListIterator
Enumeration is interface.   Use only for only legacy classes.   Like Hashtable or Vector or Properties	Iterator is interface.   Use for any (all) collection                classes. Like like ArrayList, HashSet or  Hashtable	Sub-interfaceof Iterator.   Use to traverse the List objects only.   Like ArrayList or LinkedList or Vector
Enumeration has two methods: hasMoreElements() nextElement()	Iterator has methods:  hasNext()  next()  remove()	ListIterator have methods as mention below: add(E e) hasNext() hasPrevious() next(), returns E nextIndex() previous(), returns E previousIndex() remove() set(E e)
enumerate legacy collection only in          FORWARD direction	iterate any (all) collection. only      in   FORWARD direction	ListIterator can use in  either FORWARD or  BACKWARD        directions
It unidirectional (FORWARD) directional    cursor	it unidirectional (FORWARD) directional cursor	it bi-directional (FORWARD or BACKWARD) directional          cursor
It is Fail-Safe. we can use with thread-      safe environment.	Fail Fast	Fail Fast
Does not Throw       ConcurrentModification Exception	Throw ConcurrentModification Exception	Throw ConcurrentModification Exception
Present in java.util package	Present in java.util package	Present in java.util package

Related Tutorials

• Java Basic Interview Questions
• Java interview questions part-2
• Java interview questions part-3
• Java interview questions part-4
• Java interview questions part-5

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