Java is a versatile and widely-used programming language known for its platform independence and strong support for object-oriented programming.
Java Basics cover fundamental concepts, including the structure of a Java program and how to run a simple "Hello, World!" program.
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, World!");
}
}Java Input/Output covers reading from and writing to the console and files. Here's a simple example of reading from the console:
import java.util.Scanner;
public class InputExample {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter your name: ");
String name = scanner.nextLine();
System.out.println("Hello, " + name);
scanner.close();
}
}Java Flow Control covers if statements, loops, and other control structures. Here's an example of an if-else statement:
public class IfExample {
public static void main(String[] args) {
int number = 10;
if (number > 0) {
System.out.println("Number is positive.");
} else {
System.out.println("Number is non-positive.");
}
}
}Java Operators cover arithmetic, relational, logical, and other operators. Here's an example of using arithmetic operators:
public class ArithmeticOperators {
public static void main(String[] args) {
int a = 10;
int b = 5;
int sum = a + b;
int difference = a - b;
int product = a * b;
int quotient = a / b;
int remainder = a % b;
System.out.println("Sum: " + sum);
System.out.println("Difference: " + difference);
System.out.println("Product: " + product);
System.out.println("Quotient: " + quotient);
System.out.println("Remainder: " + remainder);
}
}Java Strings cover working with text data. Here's an example of string concatenation:
public class StringExample {
public static void main(String[] args) {
String firstName = "John";
String lastName = "Doe";
String fullName = firstName + " " + lastName;
System.out.println("Full Name: " + fullName);
}
}Java Arrays cover creating and manipulating arrays. Here's an example of declaring and initializing an array:
public class ArrayExample {
public static void main(String[] args) {
int[] numbers = {1, 2, 3, 4, 5};
System.out.println("Element at index 2: " + numbers[2]);
}
}Java OOPs Concepts cover Object-Oriented Programming principles like classes, objects, inheritance, and polymorphism.
Java Inheritance allows one class to inherit properties and methods from another. Here's an example:
class Vehicle {
void start() {
System.out.println("Vehicle started.");
}
}
class Car extends Vehicle {
void accelerate() {
System.out.println("Car is accelerating.");
}
}
public class InheritanceExample {
public static void main(String[] args) {
Car car = new Car();
car.start();
car.accelerate();
}
}Java Abstraction allows you to define abstract classes and methods. Here's an example:
abstract class Shape {
abstract void draw();
}
class Circle extends Shape {
void draw() {
System.out.println("Drawing a circle.");
}
}
public class AbstractionExample {
public static void main(String[] args) {
Circle circle = new Circle();
circle.draw();
}
}Java Encapsulation is the concept of restricting access to certain components of an object and providing public methods to manipulate its state. Here's an example:
public class Student {
private String name;
private int age;
public void setName(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void setAge(int age) {
if (age > 0) {
this.age = age;
}
}
public int getAge() {
return age;
}
}Java Polymorphism is the ability of different classes to be treated as instances of the same class. Here's an example with method overriding:
class Animal {
void makeSound() {
System.out.println("Animal makes a sound");
}
}
class Dog extends Animal {
@Override
void makeSound() {
System.out.println("Dog barks");
}
}
class Cat extends Animal {
@Override
void makeSound() {
System.out.println("Cat meows");
}
}Java Constructors are special methods used to initialize objects. Here's an example with constructors:
public class Person {
String name;
int age;
// Default constructor
public Person() {
name = "John";
age = 30;
}
// Parameterized constructor
public Person(String name, int age) {
this.name = name;
this.age = age;
}
}Java Methods are blocks of code that perform specific tasks. Here's an example of a method in a class:
public class Calculator {
int add(int a, int b) {
return a + b;
}
}Java Interfaces define a contract for classes to implement. Here's an example of an interface and a class implementing it:
interface Shape {
void draw();
}
class Circle implements Shape {
@Override
public void draw() {
System.out.println("Drawing a circle.");
}
}Java Wrapper Classes provide a way to convert primitive data types into objects. Here's an example using the Integer class:
public class WrapperExample {
public static void main(String[] args) {
int primitiveInt = 42;
Integer wrappedInt = Integer.valueOf(primitiveInt);
System.out.println("Primitive Int: " + primitiveInt);
System.out.println("Wrapped Int: " + wrappedInt);
}
}Java Keywords are reserved words with special meanings in the language. Here are some common Java keywords:
abstract, class, extends, implements, static, public, private, return, if, else, for, while, new, final, this, super, switch, case, default, try, catch,throw, throws, void, int, float, double, char, boolean, and many more...
Java Access Modifiers control the visibility and accessibility of classes, methods, and variables. Here are some common access modifiers:
public, private, protected, default (package-private)
Java Memory Allocation is managed by the JVM. It includes stack and heap memory for method execution and object storage.
In Java, classes are the blueprint for creating objects. Here's an example of a simple Java class:
public class Person {
String name;
int age;
}Java packages are used to organize and group related classes. Here's an example of using packages:
package com.example.myproject;
import java.util.*;
import java.io.*;
public class MyClass {
// Class implementation
}The Java Collection Framework provides a set of classes and interfaces for working with collections of objects. Here's an example using a List:
import java.util.ArrayList;
import java.util.List;
public class CollectionExample {
public static void main(String[] args) {
List<String> names = new ArrayList<>();
names.add("Alice");
names.add("Bob");
names.add("Charlie");
}
}A List in Java is an ordered collection of elements. Here's an example of working with a List:
import java.util.ArrayList;
import java.util.List;
public class ListExample {
public static void main(String[] args) {
List<String> names = new ArrayList<>();
names.add("Alice");
names.add("Bob");
names.add("Charlie");
}
}A Queue in Java represents a collection that orders elements in a specific way. Here's an example of using a Queue:
import java.util.LinkedList;
import java.util.Queue;
public class QueueExample {
public static void main(String[] args) {
Queue<String> orders = new LinkedList<>();
orders.add("Order 1");
orders.add("Order 2");
orders.add("Order 3");
}
}A Map in Java represents a collection of key-value pairs. Here's an example of using a Map:
import java.util.HashMap;
import java.util.Map;
public class MapExample {
public static void main(String[] args) {
Map<String, Integer> population = new HashMap<>();
population.put("New York", 8500000);
population.put("Los Angeles", 4000000);
population.put("Chicago", 2700000);
}
}A Set in Java represents a collection of unique elements. Here's an example of using a Set:
import java.util.HashSet;
import java.util.Set;
public class SetExample {
public static void main(String[] args) {
Set<String> uniqueNames = new HashSet<>();
uniqueNames.add("Alice");
uniqueNames.add("Bob");
uniqueNames.add("Alice"); // Duplicate, will be ignored
}
}Java Exception Handling is a mechanism to handle runtime errors. Here's an example of catching and handling an exception:
public class ExceptionExample {
public static void main(String[] args) {
try {
int result = 5 / 0; // This will throw an ArithmeticException
} catch (ArithmeticException e) {
System.out.println("Error: " + e.getMessage());
}
}
}Java Multithreading allows multiple threads to run concurrently. Here's an example of creating and running a thread:
public class ThreadExample {
public static void main(String[] args) {
Thread thread = new Thread(() -> {
for (int i = 0; i < 5; i++) {
System.out.println("Thread " + i);
}
});
thread.start();
}
}Java Synchronization is used to control access to shared resources in a multithreaded environment. Here's an example of synchronized block usage:
public class SynchronizationExample {
private int count = 0;
public synchronized void increment() {
count++;
}
}import java.util.concurrent.*;
class Task implements Runnable {
private String name;
public Task(String name) {
this.name = name;
}
@Override
public void run() {
while (!Thread.currentThread().isInterrupted()) {
System.out.println(this.name + " is running");
try {
Thread.sleep(1000); // sleep for a second
} catch (InterruptedException e) {
Thread.currentThread().interrupt(); // Restore the interrupted status
}
}
}
public static void main(String args[]) {
ExecutorService executorService = Executors.newCachedThreadPool();
executorService.execute(new Task("Task1"));
executorService.execute(new Task("Task2"));
// Shutdown the executor service when you're done
executorService.shutdown();
}
}Java File Handling is used for reading from and writing to files. Here's a simple example of reading from a file:
import java.io.BufferedReader;
import java.io.FileReader;
public class FileHandlingExample {
public static void main(String[] args) {
try {
BufferedReader reader = new BufferedReader(new FileReader("example.txt"));
String line;
while ((line = reader.readLine()) != null) {
System.out.println(line);
}
reader.close();
} catch (Exception e) {
System.out.println("Error: " + e.getMessage());
}
}
}Java Regex (Regular Expressions) is used for pattern matching in strings. Here's an example of checking if a string matches a pattern:
import java.util.regex.Pattern;
import java.util.regex.Matcher;
public class RegexExample {
public static void main(String[] args) {
String text = "The quick brown fox jumps over the lazy dog.";
String pattern = "fox";
Pattern regex = Pattern.compile(pattern);
Matcher matcher = regex.matcher(text);
if (matcher.find()) {
System.out.println("Pattern found!");
}
}
}Java IO (Input/Output) is used for handling input and output operations. Here's an example of writing data to a file:
import java.io.FileWriter;
import java.io.IOException;
public class IOExample {
public static void main(String[] args) {
try {
FileWriter writer = new FileWriter("output.txt");
writer.write("Hello, World!");
writer.close();
} catch (IOException e) {
System.out.println("Error: " + e.getMessage());
}
}
}Java Networking is used for network communication. Here's a basic example of creating a simple client-server application:
import java.net.ServerSocket;
import java.net.Socket;
public class ServerExample {
public static void main(String[] args) {
try {
ServerSocket serverSocket = new ServerSocket(12345);
Socket clientSocket = serverSocket.accept();
// Handle client communication
} catch (Exception e) {
System.out.println("Error: " + e.getMessage());
}
}
}Java 8 introduced several features, including lambdas and the Stream API. Here's an example of using lambdas:
import java.util.ArrayList;
import java.util.List;
public class Java8Example {
public static void main(String[] args) {
List<String> names = new ArrayList<>();
names.add("Alice");
names add("Bob");
names add("Charlie");
names.forEach(name -> System.out.println("Hello, " + name));
}
}Java provides classes for working with date and time. Here's an example of formatting a date:
import java.text.SimpleDateFormat;
import java.util.Date;
public class DateTimeExample {
public static void main(String[] args) {
Date now = new Date();
SimpleDateFormat format = new SimpleDateFormat("dd/MM/yyyy HH:mm:ss");
String formattedDate = format.format(now);
System.out.println(formattedDate);
}
}JDBC is used for connecting Java applications to databases. Here's an example of database connection and retrieval:
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
public class JdbcExample {
public static void main(String[] args) {
try {
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "user", "password");
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * FROM mytable");
while (rs.next()) {
System.out.println("ID: " + rs.getInt("id") + ", Name: " + rs.getString("name"));
}
conn.close();
} catch (Exception e) {
System.out.println("Error: " + e.getMessage());
}
}
}In this Java course, you've learned a wide range of essential topics and concepts to help you become proficient in Java programming. Starting with the basics and moving on to more advanced features, you've covered everything from fundamental syntax and object-oriented principles to working with files, databases, and date and time. Java is a versatile language that finds applications in a variety of domains, from web and mobile development to enterprise-level applications. By mastering these concepts, you've gained the knowledge and skills to embark on your journey as a Java developer. Keep practicing, exploring, and building with Java to reinforce your learning. The more you code, the more comfortable and confident you'll become in using Java to create powerful and innovative software solutions. If you're eager to delve deeper into any specific area, don't hesitate to explore additional resources, courses, and projects. Java is a vast ecosystem, and there's always more to discover and learn. We wish you the best on your Java programming adventure!