Object as parameters and Returning Objects

 

🔷 Using Objects as Parameters

✅ Why Use Objects as Parameters?

Passing an object as a parameter allows one class to use the data or behavior of another class.

This supports:

• Code modularity

• Encapsulation

• Code reuse

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🧪 Example:

class Student {
    String name;
    int age;

    Student(String n, int a) {
        name = n;
        age = a;
    }

    void display() {
        System.out.println(name + " is " + age + " years old.");
    }
}

class DisplayDetails {
    void printStudent(Student s) {
        s.display(); // calling method of Student class
    }
}

public class Main {
    public static void main(String[] args) {
        Student s1 = new Student("Alice", 20);
        DisplayDetails d = new DisplayDetails();
        d.printStudent(s1);  // Passing object as parameter
    }
}

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🔄 Output:

Alice is 20 years old.

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🔷 Returning Objects from Methods

✅ What is it?

In Java, a method can return an object instead of a primitive type. This allows chaining of object operations and building modular code.

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🧪 Example:

java
class Rectangle {
    int length, width;

    Rectangle(int l, int w) {
        length = l;
        width = w;
    }

    Rectangle larger(Rectangle r2) {
        int area1 = this.length * this.width;
        int area2 = r2.length * r2.width;
        return (area1 > area2) ? this : r2; // returning the larger rectangle
    }

    void display() {
        System.out.println("Length: " + length + ", Width: " + width);
    }
}

public class Main {
    public static void main(String[] args) {
        Rectangle r1 = new Rectangle(4, 5);
        Rectangle r2 = new Rectangle(3, 6);

        Rectangle big = r1.larger(r2); // method returns an object
        System.out.print("Larger Rectangle: ");
        big.display();
    }
}

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🔄 Output:

Larger Rectangle: Length: 4, Width: 5

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🧠 Summary

Concept	Description
Objects as Parameters	Enables reuse of data and methods of an object in another class
Returning Objects	Allows method to send back an object for further operations