Technical interview questions and answers are essential for any Java Interview because Java is one of the most widely used programming languages in software development. Companies expect candidates to know OOP concepts, multithreading, exceptions, JDBC, collections, and real-time coding questions. Java interviews are commonly part of campus placements and software development roles in companies such as TCS, Infosys, Wipro, Cognizant, and Accenture. For freshers and job seekers, understanding Java concepts clearly makes it easier to clear technical rounds, online coding tests, and project discussions. This guide includes the most important and frequently asked Java interview questions with detailed explanations to help you prepare efficiently. These questions will help you gain confidence during software developer interviews and competitive placement tests.
Java professionals should deepen their expertise through J2EE development concepts and data structures fundamentals
Showing 10 of 301 questions
221. What is Overriding?
When a class defines a method using the same name, return type, and arguments as a method in its superclass, the method in the class overrides the method in the superclass.
When the method is invoked for an object of the class, it is the new definition of the method that is called, and not the method definition from superclass. Methods may be overridden to be more public, not more private.
222. What are different types of inner classes?
Nested -level classes, Member classes, Local classes, Anonymous classes
223. Are the imports checked for validity at compile time? e.g. will the code containing an import such as java.lang.ABCD compile?
Yes the imports are checked for the semantic validity at compile time. The code containing above line of import will not compile. It will throw an error saying,can not resolve symbol
symbol : class ABCD
location: package io
import java.io.ABCD;
224. Does importing a package imports the subpackages as well? e.g. Does importing com.MyTest.* also import com.MyTest.UnitTests.*?
No you will have to import the subpackages explicitly. Importing com.MyTest.* will import classes in the package MyTest only. It will not import any class in any of it's subpackage
225. What is the difference between declaring a variable and defining a variable?
In declaration we just mention the type of the variable and it's name. We do not initialize it. But defining means declaration + initialization.
e.g String s; is just a declaration while String s = new String ("abcd"); Or String s = "abcd"; are both definitions.
226. What is the default value of an object reference declared as an instance variable?
null unless we define it explicitly.
227. Can a level class be private or protected?
No. A level class can not be private or protected. It can have either "public" or no modifier. If it does not have a modifier it is supposed to have a default access.If a level class is declared as private the compiler will complain that the "modifier private is not allowed here". This means that a level class can not be private. Same is the case with protected.
228.
what type of parameter passing does Java support?
In Java the arguments are always passed by value
229. Primitive data types are passed by reference or pass by value?
Primitive data types are passed by value
230. Objects are passed by value or by reference?
Java only supports pass by value. With objects, the object reference itself is passed by value and so both the original reference and parameter copy both refer to the same object .