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
191. What if I do not provide the String array as the argument to the method?
Program compiles but throws a runtime error "NoSuchMethodError".
192. What is the first argument of the String array in main method?
he String array is empty. It does not have any element. This is unlike C/C++ where the first element by
default is the program name.
193. If I do not provide any arguments on the command line, then the String array of Main
method will be empty of null?
It is empty. But not null.
194. How can one prove that the array is not null but empty?
Print args.length. It will print 0. That means it is empty. But if it would have been null then it would have thrown a NullPointerException on attempting to print args.length.
195. What environment variables do I need to set on my machine in order to be able to
run Java programs?
CLASSPATH and PATH are the two variables.
196. Can an application have multiple classes having main method?
es it is possible. While starting the application we mention the class name to be run. The JVM will look for the Main method only in the class whose name you have mentioned. Hence there is not conflict
amongst the multiple classes having main method.
197. Can I have multiple main methods in the same class?
No the program fails to compile. The compiler says that the main method is already defined in the class.
198. Do I need to import java.lang package any time? Why ?
No. It is by default loaded internally by the JVM.
199. Can I import same package/class twice? Will the JVM load the package twice at
runtime?
One can import the same package or same class multiple times. Neither compiler nor JVM complains
about it. And the JVM will internally load the class only once no matter how many times you import the
same class.
200. What are Checked and UnChecked Exception?
A checked exception is some subclass of Exception (or Exception itself), excluding class
RuntimeException and its subclasses.Making an exception checked forces client programmers to deal with the possibility that the exception will be thrown. eg, IOException thrown by java.io.FileInputStream's read() method·Unchecked exceptions are RuntimeException and any of its subclasses. Class Error and its subclasses also are unchecked. With an unchecked exception, however, the compiler doesn't force clie