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
171. In which package are most of the AWT events that support the event-delegation
model defined?
Most of the AWT-related events of the event-delegation model are defined in the
java.awt.event package. The AWTEvent class is defined in the java.awt package.
172. What is the immediate superclass of Menu?
MenuItem
173. What is the difference between an Interface and an Abstract class?
An abstract class can have instance methods that implement a default behavior. An Interface can only
declare constants and instance methods, but cannot implement default behavior and all methods are
implicitly abstract. An interface has all public members and no implementation. An abstract class is a class which may have the usual flavors of class members (private, protected, etc.), but has some abstract methods.
174. What is the purpose of garbage collection in Java, and when is it used?
The purpose of garbage collection is to identify and discard objects that are no longer needed by a
program so that their resources can be reclaimed and reused. A Java object is subject to garbage
collection when it becomes unreachable to the program in which it is used.
175. Describe synchronization in respect to multithreading.
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 variable while another thread is in the process of using or updating same shared variable. This usually leads to significant errors.
176. Explain different way of using thread?
The thread could be implemented by using runnable interface or by inheriting from the Thread class. The former is more advantageous, 'cause when you are going for multiple inheritance..the only interface can help.
177. What are passby reference and passby value?
Pass By Reference means the passing the address itself rather than passing the value. Passby Value
means passing a copy of the value to be passed.
178. What is HashMap and Map?
Map is Interface and Hashmap is class that implements that.
179. Difference between HashMap and HashTable?
The Hash Map class is roughly equivalent to Hash table, except that it is unsynchronized and permits nulls.(Hash Map allows null values as key and value whereas Hashtable doesnt allow). HashMap does not
guarantee that the order of the map will remain constant over time. HashMap is non synchronized and
Hashtable is synchronized.