Interview Questions in Java

The Commonly Asked Interview Questions in Java are categorized topics-wise as follows:-

Fundamental Interview Questions in Java

Ques. : What is Java?

Ques. : List important features of the Java 12 release.

Ques. : List various versions of Java.

Ques. : What is the difference between Path and Classpath variables in Java?

Ques. : What are the differences between C++ and Java?

Ques. : List major features of Java.

Ques. : What is the difference between JDK, JVM, and JRE?

Ques. : Explain JIT concept in Java.

Ques. : What is WORA concept in Java?

Ques. : What do you mean by platform independence of Java?

Ques. : Explain the term Platform.

Ques. : What is the name of the Java Compiler?

Ques. : What is the name of the Java Interpreter?

Ques. : What is the extension name of Java?

Ques. : Can we override the static methods in Java?

Ques. : Explain the structure of the main method in Java.

Ques. : Why is the main method static in Java?

Ques. : Can we execute a program without the main() method in Java?

Ques. : What is the default value of the local variables?

Ques. : What are the various access specifiers in Java? Which one is applied by default in Java Program?

Ques. : Can we overload the Java main method?

Ques. : What is a ternary operator in Java?

Ques. : What is the use of the System class?

Ques. : What are the Java IDE’s?

Ques. : Is delete, next, main, exit, or null keyword in java?

Class & Object Topics Interview Questions in Java

Ques. : What is a Class & Object in Java?

Ques. : What is an inner class in Java?

Ques. : What is the anonymous inner class?

Ques. : Can we have multiple public classes in a Java source file?

Ques. : What is the abstraction in Java?

Ques. : What is the encapsulation in Java?

Ques. : What is an instance of a keyword?

Ques. : What is this keyword in Java?

Ques. : What is method overloading in Java?

Ques. : What is the final method/final class/final variable in Java?

Ques. : What is the difference between final, finally, and finalize in Java?

Ques. : What is the difference between Local variables, Instance variables, and Class variables?

Ques. : What is the static methods and variables in Java?

Ques. : Can we declare a class as static?

Ques. : What is the use of the System class?

Ques. : What is Wrapper Class in Java?

Ques. : Why are the objects immutable in Java?

Ques. : What are the advantages of Java inner classes?

Ques. : What is a nested class?

Ques. : Is there any difference between nested classes and inner classes?

Ques. : What is object cloning?

Array Topics Interview Questions in Java

Ques. : What is the Collection framework in Java?

Ques. : What are Vector and Array lists in Java?

Ques. : What are Serialization and Deserialization in Java?

Ques. : What are autoboxing and unboxing?

Constructor & Garbage Collection Topics Interview Questions in Java

Ques. : What are constructors and Garbage Collector in java? How many types of Constructors are used in Java?

Ques. : What is the default constructor?

Ques. : What is gc()?

Ques. : What is the purpose of the finalize() method?

String & String Buffer Topics Interview Questions in Java

Ques. : What is the difference between string & string buffer in Java?

Ques. : What is a String Pool?

Ques. : How many ways can we create the string object?

Ques. : What is the purpose of toString() method in Java?

Ques. : Why CharArray() is preferred over String to store the password?

Inheritance

Ques. : What is method overriding in Java?

Ques. : What is Inheritance in Java? How many types of Inheritance are implemented in Java?

Ques. : Why is multiple inheritance not supported in Java?

Ques. : What is the Super key in Java?

Ques. : What are the differences between this and the super keyword?

Package & Interface

Ques. : What is Java Package and which package is imported by default?

Ques. : What is Interface in Java?

Ques. : Can an interface implement or extend another interface in Java?

Ques. : What is the difference between abstract class and interface in Java?

Ques. : What is a package keyword in Java?

Polymorphism

Ques. : What is Polymorphism in Java? Explain its types.

Ques. : What is an abstract class in Java?

Multithreading

Ques. : What is a Thread in Java?

Ques. : What is a daemon Thread in Java?

Ques. : What is Thread Scheduler in Java?

Ques. : What do you understand by thread pool?

Ques. : What is multi-threading in Java?

Ques. : How do you make a thread in Java?

Ques. : How do you stop a thread in Java?

Ques. : What is the thread life cycle in Java?

Ques. : What is Synchronization?

Java I/O

Ques. : What is the purpose of a Transient & Volatile Variable?

Ques. : What do you understand by an IO stream?

Exception Handling

Ques. : What is Exception Handling? What is its importance?

Ques. : Explain the hierarchy of Java Exception classes.

Ques. : What is the difference between Error and Exception?

JDBC Connectivity

Ques. : What is JDBC Connectivity?

Ques. : What is the role of the JDBC Driver in connectivity?

Ques. : What are the JDBC API components?

Applets

Ques. : What is an applet in Java?

Ques. : Difference between notify() method and notifyAll() method in Java.

Advanced Java/Swing & AWT

Ques. : What is a JavaBean?

Ques. : What is RMI?

Miscellaneous

Ques. : What is Classloader & its different types in Java?

Ques. : What is Enum in Java?

Ques. : What are Java Annotations?

Ques. : What is composition in Java?

Ques. : How to run a JAR file through the command prompt?