Constructors & this

Constructor runs when you use new. Same name as class, no return type. Use it to set initial field values.

Constructors — setup new objects

Constructor runs when you use new. Same name as class, no return type. Use it to set initial field values.

If you write no constructor, Java adds a default no-arg constructor.

Real-life example: Constructor is the factory setup line — when a new phone rolls out, it gets default settings before shipping.

Constructor example

class User {
    String name;
    int age;

    User(String name, int age) {
        this.name = name;
        this.age = age;
    }
}

User u = new User("Asha", 20);

this — refer to current object

this refers to the current object. Common use: this.field = param when names clash.

this() calls another constructor in the same class — must be first line.

Real-life example: Saying "this phone" in a shop means the one in your hand, not every phone on the shelf.

this keyword

class Rectangle {
    int width, height;

    Rectangle(int width, int height) {
        this.width = width;
        this.height = height;
    }

    int area() {
        return this.width * this.height;
    }
}