Interview Questions - Java

1. What is OOP?

   Object Oriented Programming is programming paradigm, that works on the following principals:

   • Abstraction
   • Inheritance
   • Polymorphism
   • Encapsulation

2. What is Abstraction?

   Abstraction is the process of hiding certain details and showing only essential information to the user.

3. What is Polymorphism?

   Polymorphism is a concept by which we can perform a single action in different ways. ... So polymorphism means many forms.

4. What is Inheritance?

   Inheritance is a mechanism in which one object acquires all the properties and behaviors of a parent object.

5. What is immutable Object and how to create a immutable class?

1. What is JDK,JRE JVM?

2. Difference between prasing and type casting?

3. What is constructor? difference between constructor and method?

4. What are access specifiers in java ?

5. Write a program to check given string is Anagram or not?

1. What is Functional interface?

2. Abstract class Vs Interface

3. Overloading Vs Overriding

4. What is marker interface?

5. Write a program to delete duplicate elements from the array and display then ascending order

1. ArrayList Vs LinkedList

2. HashMap Vs HashTable

3. HashMap vs ConcurrentHashMap

4. How HashMap works internally?

5. Write a program to implement custom hashmap

1. Callable Vs Runnable

2. Synchronized block vs method

3. What are the different ways to create thered in java?

4. How to run multiple threads simltaniously

5. Write a program to create singleton class

1. What is design patterns?

2. finally Vs finalize

3. What are the SOLID principals?

4. What is the default capacity of LinkedList, HashMap ?

5. Write a program for builder and factory patterns

1. What is Streams?

2. Inner classes Vs Lambdas

3. What is difference between stream vs parallel stream?

4. Future vs CompletableFuture

5. Write a program to convert list of string to map where key is string and length of the string is value using streams

1. Where do you volatile keyword?

2. volatile vs transient

3. How to store custom object as key in HashMap?

4. What is exception? What are different ways to create custom exception

5. Write a program to create custom exception class?

1. What is serialaization?

2. What is serial version id?

3. this Vs Super in java?

4. What are different ways to create object?

5. Write a program to create custom annotation?

1. How garbage collectors work in JVM?

2. What is major GC and minor GC?

3. What is class loader?

4. How to increase memeory size while running java applicaation?

5. Write a program to get max paid employee of the organization using java stream?