Java Interview: Checklist

I am listing below the checklist of concepts and keywords in java which are most frequently asked in interview. Please excuse me for presenting it in a random order.

Following are the topics/keywords/concepts which require a crisp knowledge and understanding. These are basisc only.

  • JVM – About JVM, JIT compiler, Bytecode, Classloader
  • Garbage Colection – Conditions when JVM invokes garbage collection, System.gc()
  • Static and Instance initializer block
  • Datatypes – character especially
  • enum – where to declare, defining constructor, methods and variables in enum
  • OOP concepts – inheritance, polymorphism, aggregation vs Composition, abstraction
  • Multiple Inheritance in java
  • Difference/Similarities between interface and abstract class
  • Software Engineering Concepts – Coupling and Cohesion
  • String, StringBuffer and StringBuilder
  • Exception Handling – Checked vs Unchecked Exceptions, Assertion, Error, Exception Hierarchy, throw vs throws
  • final, finally and finalize
  • Method Overriding (Rules for the same)
  • Method Overloading – Covariant Return (Java5)
  • Autoboxing
  • Array – Declaring an anonymous and multidimensional array
  • Keywords like super and this
  • The Object classs – equals and hashcode methods
  • Access Specifiers – default, public , protected and private
  • Marker Interface, Wrapper Classe and Adapter Class
  • Classes like Math, StrictMath, Scanner, Console
  • Java IO: Important classes in IO, NIO.
  • Reading and writing XMLs in java. Type of parsers – SAX, DOM and STAX.
  • Java UI: AWT vs Swing, Different Layouts, Event handling, Calback methods
  • Serialization, Transient keyword
  • Multithreading – Runnable vs Thread, How to write a thread, difference between run and start method.
  • Java5 Concurrency and advanced threading – Callable, Future, Executors, Thread pooling, Locks and Conditions
  • Collection and Generics – Map, Set and List; Conventional Questions like ArrayList vs Vector, HashTable vs HashMap etc; Comparator and Comparable; Important collection classes.
  • Methods of java.util.Collections – Synchronizing a collection, Creating views
  • JDBC: The JDBC code, Type of JDBC Drivers, Type of Statements, execute, executeUpdate and executeQuery

We can discuss these further in case of queries/suggestions. Feel free to comment and add in case I missed something.

Enjoy learning,



6 thoughts on “Java Interview: Checklist

  1. A very valuable and important checklist,
    Will surely help many(including myself) for future interviews.
    Keep blogging 🙂

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