JAVA- Freshers Interview Q&A
1. What is Java?
Java is a high-level, object-oriented programming language known for its portability, platform independence, and robustness. It was developed by Sun Microsystems (now owned by Oracle Corporation) and is widely used for building various types of applications.
2. What are the main features of Java?
Java has several key features, including platform independence, strong typing, automatic memory management (garbage collection), multi-threading support, and a vast standard library.
3. Explain the difference between JDK, JRE, and JVM.
JDK (Java Development Kit): It includes tools like the Java compiler (javac) and libraries needed for Java development.
JRE (Java Runtime Environment): It provides the runtime environment required to run Java applications.
JVM (Java Virtual Machine): It is an integral part of the JRE and executes Java bytecode.
4. What is the difference between == and .equals() in Java?
== compares object references, checking if they point to the same memory location.
.equals() is a method used to compare the content or values of objects. It is often overridden in classes to provide custom comparison logic.
5.What is an Object in Java?
An object in Java is an instance of a class. It represents a real-world entity and encapsulates data (attributes) and behavior (methods).
6.Explain the concept of Inheritance in Java.
Inheritance is a fundamental OOP concept in Java that allows a subclass to inherit properties and behaviors from a superclass. It promotes code reuse and supports the “is-a” relationship.
7.What is the final keyword in Java?
The final keyword can be used to restrict further modification of classes, methods, or variables. For example, a final variable cannot be reassigned, and a final method cannot be overridden.
8. What is the purpose of the static keyword in Java?
The static keyword is used to declare members (variables and methods) that belong to the class itself rather than instances of the class. It allows you to access them without creating an object of the class.
9. What is the difference between an abstract class and an interface in Java?
An abstract class can have both abstract (unimplemented) and concrete (implemented) methods, while an interface can only have abstract methods (prior to Java 8).
A class can implement multiple interfaces, but it can inherit from only one abstract class.
10.Explain the concept of Exception Handling in Java.
Exception handling in Java is the mechanism to handle runtime errors and abnormal situations. It uses try-catch blocks to catch and handle exceptions, ensuring that the program does not terminate unexpectedly.
11.What is the Java Collections Framework?
The Java Collections Framework provides a set of classes and interfaces for working with collections of objects. It includes data structures like lists, sets, and maps, along with algorithms for common operations.
12.What is the difference between ArrayList and LinkedList in Java?
ArrayList is implemented as a dynamic array, while LinkedList is implemented as a doubly-linked list.
ArrayList is generally more efficient for random access and searching, while LinkedList is better for frequent insertions and deletions in the middle of the list.
13.What is the purpose of the synchronized keyword in Java?
The synchronized keyword is used to create synchronized blocks or methods, ensuring that only one thread can access the synchronized code at a time. It helps in achieving thread safety in multithreaded applications.
14. Explain the concept of Java Streams.
Java Streams provide a functional programming approach for processing sequences of elements (e.g., collections). They enable operations like map, filter, and reduce to be applied to data in a concise and declarative manner.
15.How do you handle exceptions in a multi-catch block in Java?
A multi-catch block allows you to catch multiple exceptions in a single catch block. For example:
try {
// Code that may throw exceptions
} catch (IOException | SQLException e) {
// Handle IOException or SQLException
}
