Part 2
Interview questions on inner classes in java for experienced covered in this post:
What is method local inner class?
- We can declare classes inside a method such types of inner
classes are called method local inner class.
- Method local inner class can be accessible only inside a
method where it is declared.
- Please refer to the below example.
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package simplifiedjava.crackedInterview; public class MethodLocalInnerClassDemo {
public static void
main(String[] args) {
MethodLocalInnerClassDemo demo
= new
MethodLocalInnerClassDemo();
demo.invokeMethodInnerClass(); }
public void
invokeMethodInnerClass() {
class
Inner{
public void
sum(int num1, int num2) {
System.out.println("Addition is "+ (num1+num2));
}
}
Inner inner
= new
Inner();
inner.sum(100, 200);
}
} |
What is static nested class?
- We can declare an inner class with a static modifier such
types of inner classes are called a static nested class.
- In the case of regular inner class without the existing
outer class object there is no chance of existing inner class object i.e.
inner class object is strongly associated with an outer class object.
- In the case of static nested classes without the existing
outer class object there may be a chance of existing inner class object.
Hence, Static nested class object is not strongly associated with an outer
class object.
- Please refer to the below example.
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package simplifiedjava.crackedInterview; public class StaticNestedClassDemo {
public static void
main(String[] args) {
Nested n
= new
Nested();
n.m1(); }
static class
Nested{
public void
m1() {
System.out.println("Nested Class.");
}
}
} |
 
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Can we declare constructor inside inner class?
- Yes, we can declare a constructor inside the inner
class.
- Please refer to the below example.
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package simplifiedjava.crackedInterview; public class Outer { public static void main(String[] args) { }
class
Inner{
int a; int b;
public
Inner(int a, int b) {
this.a
= a;
this.b
= b;
}
}
} |
Can we declare constructor inside anonymous inner class?
- No, we cannot declare a constructor inside an anonymous
inner class.
- Anonymous inner class doesn’t have any name and the
constructor name should be the same as the class name. If the class name
does not exist then how can we create a constructor?
What is the difference between Regular Inner Class and Anonymous Inner Class?
|
|
Regular Inner Class |
Anonymous Inner Class |
|
1. |
Regular inner class can implement any number of interfaces at a
time. |
Anonymous inner class can implement only one interface at a
time. |
|
2. |
Regular inner class can extend only one class and implements
multiple interfaces. |
Anonymous inner class either can extend a class or implement only
one interface. |
|
3. |
Regular inner class can have multiple constructors. |
Anonymous inner class cannot have any constructor. |
|
4. |
If the requirement is not temporary use then go for regular inner
class. |
If the requirement is temporary use then go for anonymous inner
class. |
What is the difference between Regular Inner Class and Static Inner Class?
|
|
Regular Inner Class |
Static Inner Class |
|
1. |
Outer and Inner regular classes are strongly associated with each
other. |
Outer and nested static classes are not strongly associated with
each other. |
|
2. |
Static members are not allowed. i.e. static methods and static
fields. Still, if you want to declare a static field inside the
inner class then you must declare with the final keyword as well
and assign some value to it.
e.g. static final int
c = 10; |
Static members are allowed. |
|
3. |
We cannot declare main() inside the inner class so we can’t run
directly through the command prompt. |
We can declare the main method inside the inner class so we can
call or run directly through the command prompt. |
7.
Can we access non-static class members inside static inner class?
- No, non-static class members are not allowed inside static
nested or inner class.
- Even it is applicable to the outer class as well. Inside
the static area, only static members are allowed.
How will you instantiate the Inner class?
- There are three ways to instantiate an inner class.
|
package simplifiedjava.crackedInterview; public class Outer { static int i = 0;
class
Inner{
public void
m1() {
System.out.println("Inner class m1() called. Counter = "+ ++i);
}
} } package simplifiedjava.crackedInterview; public class InstantiatingInnerClassDemo { public static void main(String[] args) {
// First way to create inner class
instance.
Outer o
= new
Outer();
Outer.Inner i
= o.new
Inner(); i.m1();
// Second way to create inner class instance.
Outer.Inner i2
= new
Outer().new
Inner(); i2.m1();
// Third way to create inner class instance.
new
Outer().new
Inner().m1();
} }
Output:
Inner class m1() called. Counter = 1
Inner class m1() called. Counter = 2
Inner class m1() called. Counter = 3
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- 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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Thank you techies for visiting this blog. I hope you enjoyed this blog and got more technical knowledge. I have tried to cover all types of questions and provided examples tested on eclipse as much as I can. Guys, please don’t just mug up the questions and answers. Try to clear your concepts with examples. Try to write a code on eclipse once you read the concepts. It will help you to memorize the concepts for a very long time. Simultaneously you will be prepared for interview programs as well. It will help you to survive in the IT sector for a long time. It may be easy to crack an interview but it's really tough to survive in the IT industry with inadequate knowledge and skills. I have collected all the questions from actual interviews attended by my friends, colleagues, college mate and classmate. I have covered frequently asked questions as well as challenging questions. I have included many programs to understand the concept thoroughly. I will try to explain the concept with the help of a real-time program in eclipse. You can share more questions which are not covered in this blog or post. Always welcome your suggestions and queries. I will definitely try to resolve it. Please comment your queries and new set of questions under the comment sections. I will create a new post for those questions.
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