Core Java Interview Questions for Beginners

 In this post, we will list out all the commonly asked Core Java interview questions for beginners.

Java array interview questions

Arrays are a fundamental part of the Java programming language and they are commonly used in many types of applications. Here are a few common Java array-related interview questions that you might encounter during a job interview:

  1. How do you declare and initialize an array in Java?
  2. How do you find the length of an array in Java?
  3. How do you copy an array in Java?
  4. How do you sort an array in Java?
  5. How do you search for an element in an array in Java?
  6. Can you explain the difference between a single-dimensional and a multi-dimensional array in Java?
  7. How do you insert an element into an array in Java?
  8. How do you remove an element from an array in Java?
  9. Can you explain how array resizing works in Java?
  10. How can you convert an array to a list in Java?

Java string interview questions

Strings are an important part of the Java programming language and they are commonly used in many types of applications. Here are a few common Java String-related interview questions that you might encounter during a job interview:

  1. Can you explain the difference between a String and a StringBuilder in Java?
  2. How do you reverse a String in Java?
  3. Can you explain the use of the StringPool in Java?
  4. How do you compare two Strings in Java?
  5. How do you convert a String to an int or double in Java?
  6. Can you explain the difference between string literal and string objects?
  7. How do you trim leading and trailing whitespace from a String in Java?
  8. How do you concatenate two or more Strings in Java?
  9. Can you explain the difference between the substring() and subSequence() methods in Java?
  10. How do you check if a String is a valid number in Java?

Java exception handling interview questions

Exception handling is an important aspect of programming in Java and it's important to understand how it works and how to use it properly. Here are a few common Java exception-handling-related interview questions that you might encounter during a job interview:
  1. Can you explain what an exception is in Java?
  2. How do you throw an exception in Java?
  3. How do you catch an exception in Java?
  4. Can you explain the difference between checked and unchecked exceptions in Java?
  5. How do you create a custom exception in Java?
  6. Can you explain the difference between the try, catch, and finally blocks in Java?
  7. How do you handle multiple exceptions in a single catch block in Java?
  8. How do you re-throw an exception in Java?
  9. Can you explain the use of the exception handling keywords 'throw' and 'throws'?
  10. How do you propagate an exception to the caller in Java?

Java thread interview questions

Threading and concurrency are important aspects of programming in Java and it's important to understand how they work and how to use them properly. Here are a few common Java thread-related interview questions that you might encounter during a job interview:

  1. Can you explain what a thread is in Java?
  2. How do you create a thread in Java?
  3. Can you explain the difference between a process and a thread in Java?
  4. How do you stop a thread in Java?
  5. How do you synchronize threads in Java?
  6. Can you explain the use of the wait() and notify() methods in Java?
  7. How do you use the Executor framework in Java?
  8. How do you use the Future and Callable interfaces in Java?
  9. Can you explain the use of the volatile keyword in Java?
  10. How do you use the ThreadPoolExecutor class in Java?

Java oops interview questions

Object-oriented programming (OOP) is a fundamental aspect of programming in Java and it's important to understand the concepts and how to use them properly. Here are a few common Java OOP-related interview questions that you might encounter during a job interview:

  1. Can you explain what inheritance is in Java?
  2. How do you define a class and an object in Java?
  3. Can you explain the use of the 'this' keyword in Java?
  4. How do you define and use constructors in Java?
  5. Can you explain the difference between overloading and overriding in Java?
  6. Can you explain the concept of polymorphism in Java?
  7. How do you define and use interfaces in Java?
  8. Can you explain the use of the final keyword in Java?
  9. Can you explain the difference between encapsulation and abstraction in Java?
  10. How do you use the abstract class and interface together?

Java collections interview questions

  1. Can you explain the difference between a list and a set in Java?
  2. How do you define and use a map in Java?
  3. Can you explain the use of the Iterator interface in Java?
  4. How do you sort a collection in Java?
  5. How do you convert a list to an array in Java?
  6. Can you explain the difference between a HashMap and a TreeMap in Java?
  7. How do you remove an element from a collection in Java?
  8. Can you explain the use of the Comparable and Comparator interfaces in Java?
  9. How do you perform a binary search on a collection in Java?
  10. Can you explain the use of the LinkedList and ArrayDeque classes in Java?

Java generics interview questions

Generics are a powerful feature of the Java programming language that allows you to write type-safe code while being more flexible and reusable. Here are a few common Java generics-related interview questions that you might encounter during a job interview:

  1. Can you explain what generics are in Java?
  2. How do you define and use a generic class in Java?
  3. Can you explain the use of wildcard types in Java generics?
  4. How do you use bounds with generics in Java?
  5. Can you explain the use of the diamond operator in Java?
  6. How do you use generics with interfaces in Java?
  7. Can you explain the use of type erasure in Java generics?
  8. How do you define and use a generic method in Java?
  9. How do you use generics with arrays in Java?
  10. Can you explain the use of the <? super T> and <? extends T> bounds in Java generics?

Comments