Core java interview questions for 3 years experience Covered in this post:
Can you declare constructor static,
final, abstract and synchronized?
- We cannot declare constructor static, final, abstract and
synchronized.
- Purpose of all four keywords given above is different.
How does an object become eligible for garbage collection?
- Object can be made eligible for garbage collection when there is no single
reference variable pointing to it.
- There are three ways objects can make eligible for garbage
collection.
1. When an object goes out of scope.
2. Objects reference variable explicitly assigned a null
value.
3. Reinitialize the reference variable.
 
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How thread communicate each other.
- Basically, wait(), notify(), notifyAll() methods are using by threads to
communicate with each other. But these methods belong to java.lang.Object
class.
Can you tell me what are the Serializable and Externalizable?
- Serializable and Externalizable are the Interfaces.
- Serializable interface Externalizable interface belongs to java.io. package
Can we declare outer class is private?
- No, the Outer class cannot be private. An outer class should be public.
What is Inner Class?
- A class declared inside another class is called 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{
}
} |
What is ArrayList and what are the characteristics of ArrayList?
- ArrayList is a growable array. No need to declare the size
like an array.
- ArrayList is introduced in Java 1.2.
- ArrayList is the best choice if you want to perform
retrieval, sorting and searching operations.
- ArrayList is the worst choice if you want to perform an insertion and
deletion operation.
- Characteristics:
1. Resizable and Growable Array.
2. Duplicate Allowed.
3. Insertion Order Preserved.
4. Heterogeneous (Different type of Object) Allowed.
5. NULL insertion is possible.
6. Not a Thread-safe.
7. ArrayList is Serializable because this class implements Serializable
interface.
8. ArrayList is Clonable because this class implements Clonable
interface.
- Randomly Accessible because ArrayList implements RandomAccess interface.
What is the abstract method defined in Function functional interface?
- Function interface has defined apply() as an abstract
method.
- Please refer to the below example for syntax.
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@FunctionalInterface
public interface
Function<T, R> {
R apply(T t);
} |
What is the return type of apply method in Function functional interface?
- The return type of apply() method is any object.
- Java doc denoted as R(Return Type).
- Please refer to the below example.
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@FunctionalInterface
public interface
Function<T, R> {
R apply(T t);
} |
What is Bi-Predicate functional
interface?
-
Bi-Predicate is used to perform a particular condition
check.
- Predicate can be used like if condition. It will always return a Boolean
value.
-
Bi-Predicate accepts two arguments and return a Boolean
value.
-
Please refer to the below example.
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@FunctionalInterface public interface BiPredicate<T, U> {
} |
- 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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