Java Basics for Beginners
Java, a high-level programming language, was conceived by Sun Microsystems (now a part of Oracle Corporation) in 1995. Its platform-independence makes it unique – write your Java code on one platform, and it can run anywhere that has Java Runtime Environment (JRE).
2. The structure of a Java Program:
Here’s an elementary Java program:
public class Greeting {
public static void main(String[] args) {
System.out.println("Hello, World!");
}
}
In this code, Greeting is a class. The main component of a Java application is its class. The main() method, present inside the class, serves as the program’s entry point.
3. Data Types and Variables:
Java comprises several data types:
- int for whole numbers (e.g., 7, 42, 0)
- double for numbers with decimals (e.g., 3.14, -0.99)
- char for individual characters (e.g., ‘b’, ‘Z’)
- boolean for binary values (true/false)
- String for a chain of characters (e.g., “Good Morning!”)
You can use variables to hold values:
int myAge = 21;
String myName = "John Doe";
4. Operators in Java:
Java includes various types of operators: arithmetic (+, -, *, /, %), comparison (<, >, <=, >=, ==, !=), and logical (&&, ||, !).
5. Control Flow Statements:
Java provides several control flow structures like if conditions, for and while loops. For example:
if (myAge > 18) {
System.out.println("Adult");
} else {
System.out.println("Minor");
}
for (int i = 1; i <= 5; i++) {
System.out.println(i);
}
while (myAge < 25) {
System.out.println(myAge);
myAge++;
}
6. Arrays in Java:
An array lets you store multiple values in a single variable. Here’s the way to declare an array:
double[] myGrades = new double[5]; // A double array of size 5
7. Methods:
Methods (or functions) in Java are blocks of code designed to perform specific tasks.
public double calculateAverage(double num1, double num2) {
return (num1 + num2) / 2;
}
8. Object-Oriented Programming (OOP):
Java leverages object-oriented programming principles, enabling it to depict concepts as “objects” that pair data fields (attributes) with procedures known as methods.
You use classes to create objects in OOP. A class is like a template for creating objects. Here’s a simple class definition:
public class Cat {
// Attributes or fields
String breed;
String color;
// Behavior or method
void meow() {
System.out.println("Meow Meow");
}
}
The foundational OOP concepts in Java are:
- Inheritance: A class can adopt properties (fields and methods) from another class.
- Encapsulation: Binds together code and the data it manipulates into a single unit, such as a class.
- Polymorphism: Allows methods to perform varied tasks based on the object they interact with.
- Abstraction: Reveals only necessary information to the user, hiding internal complexity.
Demo Day 1 Video:
Conclusion:
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