Interview questions on inner classes in java for experienced

 Part 1

Interview questions on inner classes in java for experienced covered in this post:

        What is Inner Class?

-          A class declared inside another class is called Inner class.

-          Please refer to the below example.

package simplifiedjava.crackedInterview;  public class Outer {        public static void main(String[] args) {                  }            class Inner{                  } }

 

        What is the purpose of Inner classes?

-          It is a way of logically grouping classes that are only used in one place: If a class is useful to only one other class, then it is logical to embed it in that class and keep the two together. Nesting such "helper classes" makes their package more streamlined. 

-          It increases encapsulation: Consider two top-level classes, A and B, where B needs access to members of A that would otherwise be declared private. By hiding class B within class A, A's members can be declared private and B can access them. In addition, B itself can be hidden from the outside world.

 

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        What are the advantages and disadvantages of Inner class?

-          Advantages:

1.       An inner class is used to develop maintainable code because they logically group classes and interface in one place.

2.       Easy access as the inner classes is implicitly available in the outer class.

3.       Inner classes represent a special type of relationship which allows access to all members.

-          Disadvantages:

1.       Code complexity increases.

2.       Multiple inner classes may decrease the performance.

 

        Can we declare a class inside a method?

-          Yes, we can declare the class inside a method which is called method local inner class.

 

        Can we declare outer class is private?

-          No, the Outer class cannot be private. An outer class should be public. 

 

        Can we declare outer class as a Default or Strictfp or Final?

-          Yes, all three keywords are applicable to the outer class.

 

        Can we declare inner class as a private?

-          Inner class can be declared as a private but cannot declare outer class as a private class.

 

        Can we declare static inner class?

-          We can declare an inner class as a static class.

 

        What is the difference between Normal class and Inner class?

	Normal Class / Outer Class	Inner Class
1.	An outer class can be instantiated without instantiating an inner class.	Non-static Inner class cannot be instantiated without instantiating an outer class.
2.	The outer class does not totally depend on the inner class.	An inner class totally depends on the outer class.
3.	An outer class cannot be private.	An inner class can be private.
4.	An outer class cannot be static.	An inner class can be static.
5.	An outer class cannot be protected.	An inner class can be protected.

 

        What is Anonymous Inner Class?

-          We can declare inner classes without name such type of inner classes are called Anonymous Inner class.

-          Anonymous inner class can use for instant use.

-          Anonymous inner class can extend a class and implement an interface.

-          Anonymous inner class can be declared as a method argument.

-          Please refer to below example for an anonymous inner class.

package simplifiedjava.crackedInterview;  public class AnnonymousInnerClassDemo {        public static void main(String[] args) {                        AnnonymousInnerClassDemo inner = new AnnonymousInnerClassDemo(){              };       } }

• Java interview questions and answers all MNC - Click here

• Basic core java interview questions and answers for freshers - Click here

• Core java interview questions for 3 years experience - Click here

• Core java interview questions and answers for 3-5 years exp - Click here

• Core java interview questions and Answers for 5 - 7 Years exp - Click here

• Basic Java Interview Questions and Answers - Click here

• Java interview questions and answers on oops - Click here

• Java interview questions and answers on Strings - Click here

• Java interview questions on exception handling - Click here

• Interview questions on multithreading in java for experienced - Click here

• Interview questions on serialization in java for experienced - Click here

• Interview questions on inner class in java for experienced - Click here

• Interview questions on Collections in java for experienced - Click here

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