WikiGalaxy
Introduction to Java
What is Java?
Java is a high-level, class-based, object-oriented programming language designed to have as few implementation dependencies as possible. It is widely used for building enterprise-scale applications.
Setting Up Java Development Environment
Installing JDK
To start developing in Java, you need to install the Java Development Kit (JDK). The JDK contains the Java Runtime Environment (JRE), an interpreter/loader (Java), a compiler (javac), an archiver (jar), a documentation generator (Javadoc), and other tools needed in Java development.
Writing Your First Java Program
Hello World Example
The first step in learning any programming language is writing a simple program that prints "Hello, World!" to the console. This helps you understand the basic syntax of the language.
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, World!");
}
}
Understanding Java Syntax
Basic Syntax
Java syntax is the set of rules defining how a Java program is written and interpreted. It includes the use of classes, methods, variables, data types, and operators.
Variables and Data Types
Declaring Variables
Variables are containers for storing data values. Java has different types of variables, such as int, float, char, and String. Each variable has a specific data type that determines the size and layout of the variable's memory.
int myNum = 5;
float myFloatNum = 5.99f;
char myLetter = 'D';
String myText = "Hello";
Java Operators
Arithmetic Operators
Java provides various operators for performing arithmetic operations such as addition, subtraction, multiplication, and division.
int sum = 100 + 50;
int difference = 100 - 50;
int product = 100 * 50;
int quotient = 100 / 50;
Control Flow Statements
If-Else Statements
Control flow statements are used to control the order of execution of statements in a program. The if-else statement allows conditional execution of code blocks.
int number = 10;
if (number > 0) {
System.out.println("Positive number");
} else {
System.out.println("Negative number");
}
Loops in Java
For Loop
Loops are used to execute a block of code repeatedly. The for loop is commonly used when the number of iterations is known.
for (int i = 0; i < 5; i++) {
System.out.println(i);
}
Java Methods
Defining Methods
Methods are blocks of code that perform a specific task and are executed when called. They help in code reusability and organization.
public class MyClass {
public static void myMethod() {
System.out.println("Hello from a method");
}
public static void main(String[] args) {
myMethod();
}
}
Object-Oriented Programming
Classes and Objects
Java is an object-oriented programming language, which means it uses objects and classes to structure the code. A class is a blueprint for objects, and an object is an instance of a class.
public class Car {
String color;
int year;
public Car(String color, int year) {
this.color = color;
this.year = year;
}
}
public class Main {
public static void main(String[] args) {
Car myCar = new Car("Red", 2020);
System.out.println("Car color: " + myCar.color);
}
}
