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
131. What is the difference between the >> and >>> operators?
The >> operator carries the sign bit when shifting right. The >>> zero-fills bits that have been shifted out.
132. what is a transient variable?
A transient variable is a variable that may not be serialized.
133. Why do threads block on I/O?
Threads block on i/o (that is enters the waiting state) so that other threads may execute
while the i/o Operation is performed.
134. How are Observer and Observable used?
Objects that subclass the Observable class maintain a list of observers. When an
Observable object is updated it invokes the update() method of each of its observers to
notify the observers that it has changed state. The Observer interface is implemented by
objects that observe Observable objects.
135. What is synchronization and why is it important?
With respect to multithreading, synchronization is the capability to control the access of
multiple threads to shared resources. Without synchronization, it is possible for one
thread to modify a shared object while another thread is in the process of using or
updating that object's value. This often leads to significant errors.
136. What is the preferred size of a component?
The preferred size of a component is the minimum component size that will allow the
component to display normally.
137. What is the Collections API?
The Collections API is a set of classes and interfaces that support operations on
collections of objects.
138. Which characters may be used as the second character of an identifier,
but not as the first character of an identifier?
The digits 0 through 9 may not be used as the first character of an identifier but they may
be used after the first character of an identifier.
139. How does Java handle integer overflows and underflows?
It uses those low order bytes of the result that can fit into the size of the type allowed by
the operation.
140. What is the Vector class?
The Vector class provides the capability to implement a growable array of objects