Java Questions For Freshers
Important Java Concepts for Freshers
Java is a popular programming language used for developing various applications ranging from web applications to mobile applications. As a Fresher, it is essential to have a good understanding of fundamental concepts like basic syntax, data types, control structures, and object-oriented programming principles in Java. Some common Java questions that are asked in the interviews for freshers include questions about basic concepts, data types, looping structures, arrays, inheritance, polymorphism, exception handling, and string manipulation. Preparing for these questions can help you showcase your knowledge and skills in Java and increase your chances of securing a job as a Java developer.
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1 - What is Java?
Java is a high-level, object-oriented programming language used for developing a variety of applications, including web, mobile, and desktop. It was developed by James Gosling at Sun Microsystems in 1995.
2) What is the difference between JDK, JRE, and JVM?
JDK (Java Development Kit) is a software development kit that contains tools for developing, debugging and monitoring Java applications. JRE (Java Runtime Environment) is a software package that provides the runtime environment for Java applications to run. JVM (Java Virtual Machine) is a virtual machine that executes Java bytecode. In simpler terms, JDK is used for developing Java applications, JRE is used for running them, and JVM is the engine that runs the code.
3) What is the significance of the main() method in Java?
The main() method acts as the entry point for a Java program. It is mandatory for every Java program to have a main() method, and it serves as the starting point for the execution of the program.
4) What is an object-oriented programming language?
An object-oriented programming language is a programming language that uses objects and their interactions to design applications. It follows the concepts of encapsulation, polymorphism, and inheritance to achieve code reusability, maintainability, and extensibility.
5) What is the difference between an object and a class?
A class is a blueprint or a template for creating objects. It contains the properties and behaviors that define the object's structure. An object, on the other hand, is an instance of a class that has its own unique set of values for the class's properties.
6) What is the difference between an interface and an abstract class?
An interface is a collection of abstract methods (methods without implementation) that can be implemented by a class. An abstract class, on the other hand, is a class that contains both abstract and non-abstract methods. In Java, a class can only extend one abstract class, but it can implement multiple interfaces.
7) What is a constructor and its purpose?
A constructor is a special method used for initializing objects. It has the same name as the class and is responsible for assigning initial values to an object's properties. The purpose of a constructor is to ensure the object is in a valid and usable state when it is created.
8) What is a package in Java?
A package is a collection of related classes and interfaces. It helps to organize code and avoid naming conflicts. Java provides a default package, but it is recommended to use a specific package name for better code management.
9) What is the difference between a static and non-static method in Java?
A static method belongs to a class, and it can be called without creating an instance of the class. On the other hand, a non-static method belongs to an object, and it can only be called after creating an instance of the class.
10) What is an exception in Java?
An exception is an abnormal condition that occurs during the execution of a program, disrupting the normal flow of the program. It can occur due to different reasons, such as bad input, resource unavailability, and coding errors.
11) What is a try-catch block?
A try-catch block is used for exception handling in Java. The code within the try block is monitored, and if an exception occurs, it is caught by the catch block, where the appropriate action can be taken.
12) What is a loop in Java?
A loop is a programming construct that allows a set of instructions to be executed repeatedly until a certain condition is met. Java provides different types of loops, including for, while, and do-while loops.
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13) What is the difference between a break statement and a continue statement?
A break statement is used to terminate a loop and transfer control to the statement following the loop. On the other hand, a continue statement is used to skip the current iteration of a loop and move to the next iteration.
14) What is the purpose of the final keyword?
The final keyword is used to declare a constant variable, a final class, or a final method. A final variable cannot be reassigned a new value once it is initialized, a final class cannot be inherited, and a final method cannot be overridden.
15) What is the difference between a StringBuilder and a StringBuffer?
A StringBuilder is a mutable data type used for creating and manipulating strings. It is not synchronized, making it faster but not thread-safe. A StringBuffer, on the other hand, is a thread-safe version of StringBuilder, which makes it slower but ensures data integrity in a multi-threaded environment.
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