Java is a high-level, object-oriented programming language used to build web apps, mobile applications, and enterprise software systems.
- Known for its Write Once, Run Anywhere capability, which means code written in Java can run on any device that supports the Java Virtual Machine (JVM).
- Syntax and structure is similar to C-based languages like C++ and C#.
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Why Learn Java?
- Used to build Android apps, desktop and web apps, enterprise backend systems, and cloud-based software.
- In high demand with many job opportunities in software development.
- Has popular frameworks like Spring and Hibernate which makes it powerful for enterprise applications.
- Supports object-oriented programming for clean and reusable code.
- It runs on all platforms Windows, Mac, and Linux using the JVM.
- Top companies like Amazon, Netflix, and LinkedIn use Java.
Hello World Program
Here is a simple Java program that prints "Hello World".
Java
public class Geeks {
public static void main(String args[])
{
System.out.println("Hello World");
}
}
Basics
Java basics form the foundation of your programming journey, covering essential concepts like syntax, data types, variables, loops, and conditionals.
Methods
Java methods are reusable blocks of code that perform specific tasks and help organize your program. They improve code readability, reduce repetition, and make debugging easier.
Arrays
Java arrays are containers that store multiple values of the same data type in a single variable. They provide an efficient way to manage and access collections of data using index-based positions.
Strings
Java Strings represent sequences of characters and are widely used in text processing. They are immutable, meaning once created, their values cannot be changed.
Regex
Java Regex (Regular Expressions) allows pattern matching and text manipulation using the java.util.regex package. It is powerful for validating, searching, and replacing strings based on specific patterns.
OOP Concepts
Java follows the Object-Oriented Programming (OOP) paradigm, which organizes code into classes and objects. Core OOP principles like inheritance, encapsulation, polymorphism, and abstraction make Java modular and scalable.
Interfaces
Java interfaces define a contract that classes must follow, specifying method signatures without implementations. They enable abstraction and support multiple inheritance in Java through a clean, structured approach.
Exception Handling
ava Exception Handling is a mechanism to handle runtime errors, ensuring the program runs smoothly without crashing. It uses keywords like try, catch, throw, throws, and finally to manage exceptions.
Memory Allocation
Java Memory Allocation refers to how memory is assigned to variables, objects, and classes during program execution. It involves stack and heap memory, with the JVM managing allocation and garbage collection automatically.
Collections
Java Collections provide a framework for storing and manipulating groups of objects efficiently. It includes interfaces like List, Set, and Map, along with classes like ArrayList, HashSet, and HashMap.
Lambda Expressions and Streams
Java Streams and Lambda Expressions simplify data processing by enabling functional-style operations on collections. Lambdas provide concise syntax for anonymous functions, while Streams allow efficient filtering, mapping, and reduction of data.
Multithreading and Synchronization
Java Multithreading allows concurrent execution of two or more threads, enabling efficient CPU utilization and faster program performance. It is commonly used for tasks that required parallel processing and responsiveness from multiple ends.
File Handling
Java File Handling enables programs to create, read, write, and manipulate files stored on the system. It uses classes from the java.io and java.nio packages for efficient file operations.
Networking
Java Networking enables communication between devices over a network using classes from the java.net package. It supports protocols like TCP and UDP for building client-server applications and data exchange.
Java Database Connectivity(JDBC)
Interview Questions
Prepare for Java interviews with these commonly asked questions, covering core concepts, OOP, collections, multithreading, exception handling, and frameworks like Spring and Hibernate.
Important Links
Practice
Introduction to Java
Writing First Program in Java
Variables and Primitive DataTypes
Non Primitive DataTypes
Type Conversion in Java
Input in Java
