Basics before Android Development
Basics of Programming using Java
1.1 Variables, Data Types, Operators: In Java, variables are used to store data. Data types specify the kind of value a variable can hold, such as integers, floating-point numbers, or characters. Operators are used to perform operations on variables.
Example Code:
public class VariablesExample {
public static void main(String[] args) {
int num1 = 10;
double num2 = 5.5;
char letter = 'A';
int sum = num1 + (int) num2; // Casting double to int
System.out.println("Sum: " + sum);
System.out.println("Letter: " + letter);
}
}
Output:
Sum: 15 Letter: A
1.2 Control Structures: if, else, switch and loops: Control structures allow you to control the flow of your program. Conditional statements like "if" and "else" help make decisions, while loops allow you to repeat a block of code.
Example Code:
public class ControlStructuresExample {
public static void main(String[] args) {
int age = 18;
if (age >= 18) {
System.out.println("You are an adult.");
} else {
System.out.println("You are a minor.");
}
for (int i = 1; i <= 5; i++) {
System.out.println("Iteration " + i);
}
int dayOfWeek = 3;
switch (dayOfWeek) {
case 1:
System.out.println("It's Monday.");
break;
case 2:
System.out.println("It's Tuesday.");
break;
case 3:
System.out.println("It's Wednesday.");
break;
case 4:
System.out.println("It's Thursday.");
break;
case 5:
System.out.println("It's Friday.");
break;
case 6:
System.out.println("It's Saturday.");
break;
case 7:
System.out.println("It's Sunday.");
break;
default:
System.out.println("Invalid day of the week.");
break;
}
}
}
Output:
You are an adult. Iteration 1 Iteration 2 Iteration 3 Iteration 4 Iteration 5 It's Wednesday.
1.3 Functions and Object-Oriented Concepts: Functions are reusable blocks of code that can be called multiple times. Object-oriented concepts involve creating classes and objects to organize and structure your code.
Example Code:
class Circle {
double radius;
double calculateArea() {
return Math.PI * radius * radius;
}
}
public class OOPExample {
public static void main(String[] args) {
Circle myCircle = new Circle();
myCircle.radius = 5.0;
double area = myCircle.calculateArea();
System.out.println("Area: " + area);
}
}
Output:
Area: 78.53981633974483
1.4 Polymorphism and Inheritance: Polymorphism allows objects of different classes to be treated as objects of a common superclass. Inheritance enables a class to inherit properties and behaviors from another class.
Example Code:
class Shape {
void draw() {
System.out.println("Drawing a shape");
}
}
class Circle extends Shape {
void draw() {
System.out.println("Drawing a circle");
}
}
class Square extends Shape {
void draw() {
System.out.println("Drawing a square");
}
}
public class PolymorphismExample {
public static void main(String[] args) {
Shape[] shapes = { new Circle(), new Square() };
for (Shape shape : shapes) {
shape.draw();
}
}
}
Output:
Drawing a circle Drawing a square
1.5 Encapsulation: Encapsulation refers to the practice of hiding internal details of an object and providing a controlled interface to interact with it.
Example Code:
class Student {
private String name;
private int age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
if (age > 0) {
this.age = age;
}
}
}
public class EncapsulationExample {
public static void main(String[] args) {
Student student = new Student();
student.setName("Alice");
student.setAge(-20); // This won't change the age due to validation in the setter
System.out.println("Name: " + student.getName());
System.out.println("Age: " + student.getAge());
}
}
Output:
Name: Alice Age: 0
1.6 Static Classes and Functions:_ Static members belong to the class rather than instances of the class. Static methods and variables can be accessed without creating an instance of the class.
Example Code:
class MathUtils {
static int add(int a, int b) {
return a + b;
}
}
public class StaticExample {
public static void main(String[] args) {
int sum = MathUtils.add(5, 3);
System.out.println("Sum: " + sum);
}
}
Output:
Sum: 8
Pattern We can use nested loop to print patterns in Java. Here is an example to print a pattern of numbers:
public class PatternExample {
public static void main(String[] args) {
int rows = 5;
for (int i = 1; i <= rows; i++) {
for (int j = 1; j <= i; j++) {
System.out.print(j + " ");
}
System.out.println();
}
}
}
Output:
1 1 2 1 2 3 1 2 3 4 1 2 3 4 5
Practice Exercise:
solve the following pattern using Java programming language:
Section 2: Introduction to Version Control: Git and GitHub
2.1 Introduction to Git and GitHub:_ Version control helps track changes to your code over time. Git is a widely used version control system, and GitHub is a platform that hosts repositories and enables collaboration.
2.1 Setting Up Git and GitHub for Version Control:_ Before we delve into more advanced programming concepts, let's ensure you have the tools to manage your code effectively using version control. Follow these steps to set up Git and connect it with GitHub on your Windows PC:
a. Download and Install Git:
I. Visit the official Git website at https://git-scm.com/download/win. II. Download the installer for Windows. III. Run the installer and follow the installation instructions.
b. Configure Git: Open the command prompt or Git Bash (included with Git installation) and configure your identity by running the following commands. Replace "Your Name" and "your.email@example.com" with your actual name and email.
git config --global user.name "Your Name" git config --global user.email your.email@example.com
c. Generate SSH Key: To securely connect with GitHub, you can use SSH keys. Generate a new SSH key using the following command:
ssh-keygen -t ed25519 -C "your.email@example.com"
d. Press Enter to save the key in the default location
(~/.ssh/id_ed25519) and create a passphrase for added security if
desired.
e. Add SSH Key to GitHub:
I. Copy your public SSH key to the clipboard:
II. clip < ~/.ssh/id_ed25519.pub
III. Visit your GitHub account settings (https://github.com/settings/keys).
IV. Click on "New SSH Key" and paste the copied key.
f. Test the Connection: To verify that everything is set up correctly, run the following command in Git Bash or the command prompt:
ssh -T git@github.com
g. You should see a message confirming your connection to GitHub.
h. Creating a Repository on GitHub:
a. Log in to your GitHub account. b. Click the "+" button in the top-right corner and select "New Repository." c. Give your repository a name, choose settings as needed, and click "Create repository."
i. Pushing Code to GitHub: Once you've made changes to your code, you can push it to your GitHub repository using commands like:
git add . git commit -m "Add initial code" git remote add origin "repository URL" git push -u origin main
2.2 Basic Git Commands:
-
git init: Initialize a new Git repository. -
git ``add <filename>: Stage changes for commit. -
git commit -m "Commit message": Commit staged changes. -
git status: View the status of your repository. -
git log: View commit history.