Core Java Most Commonly Asked Interview Questions.

  • What are the differences between JDK, JRE, JVM, JIT?
  • Which JDK version you used in your project?
  • What are the Java 5, 7, 8 features?
  • How to migrate the java 7 project to java 8 version?
  • How to write Documentation Comment?
  • What is Class & Object?
  • What is OOPS and what are their pillars?What is Abstraction, PolymorphismInheritance and Encapsulation?
  • How did you implemented OOPS concept in your project?
  • What is static in java?
  • What is final in java?
  • Why can't a local variable have default value?
  • What is Constructor and what are the differences between Constructor and Method?
  • What is Constructor Chaining in Java?
  • What are the things happening internally at memory level when we create an object in java? Explain Object creation steps.
  • What is Static Polymorphism or Compile Time Polymorphism or Overloading or Early binding?
  • What is Dynamic Polymorphism or Run Time Polymorphism or Overriding or Late Binding?
  • What are the differences between Overloading and Overriding?
  • Can we have different return type in overloading/overriding?
  • Can we override static method ? Justify for YES or NO.
  • How to restrict the methods from overriding?
  • What are the difference between Interface and Abstract Class?
  • Why Abstract Classes are there in Java?
  • What is static import?
  • What is path, classpathWhat are the differences between them? How to set the path and classpath?
  • What is jar-war-ear? Differences among them? How to create them? How to execute them?
  • What is Diamond problem in Multiple Interitance?
  • What is Has-A and Is-A relationship in java?
  • Difference between Association vs Inheritance and Aggregation vs Composition.
  • What is Coupling and Cohesion?
  • What are the importance of Inner class in java, why did vendors design it?
  • What is hashcode?
  • Difference between equals method and == operator?
  • What is cloning, Types of cloning,Difference between them Write the code to implement Deep Clone?
  • What is garbage collection in java, Explain in detail.
  • What are the differences between String, StringBuilder & StringBuffer?
  • What is the difference between creating the string object with new operator and without new operator?
  • What is String Constant Pool and Why String uses it?
  • Why String is final, Immutable?
  • Name the five important methods of String that you used so frequently.
  • What is Auto - Boxing & Auto - Unboxing?

  • What are BigInteger and BigDecimal classes in java? 
  • What are the differences among Heap, Stack and Method Area?
  • What is design pattern?
  • How to create singleton design pattern?
  • What is Immutable Class and how to design Immutable class?
  • How to break the singleton design pattern?
  • What is class loader, How many types of class loaders are available in java?
  • In how many ways we can create the object of class?
  • What is difference between Compile Time and Runtime Exception?
  • How to create user defined exception?
  • What are the differences between final, finally & finalize?
  • What are the differences between throw & throws?
  • Which is  preferable between finally block and finalize method and why?
  • Explain the Exception throwing rules while overriding the methods.
  • In how many ways we can create the thread? Which one is preferable and why?
  • Explain the thread life cycle.
  • What are the differences between Sleep method and Wait method?
  • Why wait and notify methods are available in Object class while being used in context of Thread Class?
  • What is Synchronization? In how many ways we can apply Synchronization?Explain in detail.
  • What is Deadlock? write the code for Deadlock.
  • What is Consumer & Producer Problem? Write the code for the same. 
  • What is thread pooling? explain it with codes?
  • What is join method?Write the code to explain.
  • What is Daemon Thread? How to create Daemon Thread?
  • What is difference between stop & yield method in java?
  • What is volatile keyword in java?
  • What is collection? Draw the hierarchy of collection.
  • What are the differences between Collection, Collection Framework & Collections?
  • Which collection you used in your project and why?
  • How does Set collection rejects the duplicate elements?
  • What are the differences between:
  •    Array vs ArrayList.             
  •    ArrayList vs LinkedList.
  •    List vs Set.
  •    HashSet vs TreeSet.
  •    Iterator vs ListIterator.
  •    Comparable vs Comparator.
  • What is Hashing Technique, How to avoid Collision in Hashing?
  • Explain the internal Implementation of HashMap & LinkedHashMap?
  • What are the differences between peak & poll of Queue?
  • What is Concurrent Collection?
  • What is Generic?
  • What is Serialization? What is Transient? Can we serialize static variable?
  • What is Reflection?
  • What are the differences between creating the object using  newInstance method  and new operator?

Coding Round.
  • Prime Number Checking.
  • One Sorting Code.
  • Second Highest Number.
  • Star Pattern Printing Program.
  • Factorial.
  • Reverse String.
  • Reverse Number.
  • Count the occurrence of each character in given string.
  • Consumer Producer Code.
  • Dead Lock Code.
  • Palindrome.
  • Armstrong.
  • Creation of Thread Pool.
  • Temperature Conversion.
Various Company's Interview Questions Link below.
For Answers click on this link Get Answer

Comments

  1. Thank you for the list, very helpful...

    ReplyDelete
  2. The questions what ever listed, i have just followed blindly and went for my first interview, finally i cracked the and I'm in. Its all because of you.

    ReplyDelete
    Replies
    1. Hi Ranjitha,
      Thank you so much for the feedback.
      Glad to know that it helped you alot.

      Delete

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