Java Day 7: Methods and Basic Object-Oriented Concepts

Goal of this Day

Today you will learn:

• How to define and call methods
• How to use parameters and return values
• The basics of classes and objects

By the end, you will be able to structure your code using methods and create simple objects.

Step 1: Defining and Calling Methods

A method is a block of code that performs a specific task.

public static int add(int x, int y) {
    return x + y;
}

To call a method:

int result = add(5, 3);

Explanation:

• int → return type
• x, y → parameters
• return → sends the result back

Step 2: Parameters and Return Values

Parameters allow you to pass data into methods.

Return values send results back to the caller.

public static int multiply(int a, int b) {
    return a * b;
}

Step 3: Introduction to Classes and Objects

Java is an object-oriented programming language.

• A class is a blueprint
• An object is an instance of a class

Example:

class Dog {
    String name;
    int age;

    void bark() {
        System.out.println("Woof!");
    }
}

Practice

public class Calculator {
    public static int add(int x, int y) {
        return x + y;
    }

    public static void main(String[] args) {
        int sum = add(5, 3);
        System.out.println("Sum: " + sum);
    }
}

Exercise

Create a class Dog with attributes and a method.

Steps:

• Create a class Dog
• Add attributes name and age
• Create a method bark()
• Create an object and call the method

Example:

public class Dog {
    String name;
    int age;

    void bark() {
        System.out.println("Woof!");
    }

    public static void main(String[] args) {
        Dog myDog = new Dog();
        myDog.name = "Buddy";
        myDog.age = 3;

        myDog.bark();
    }
}