Notes

this keyword is a reference to the current object of the class. it is used to resolve ambiguity between instance variables and parameters or to invoke methods/constructors of the current class.

referring to instance variable

class Person  Person {
    String name;
    int age;

    Person(String name, int age) {
        this.name = name; // 'this.name' refers to the instance variable, 'name' to the parameter
        this.age = age;
    }
}

invoking another constructor

class Person {
    String name;
    int age;

    Person(String name) {
        this(name, 0); // Calls the constructor with two parameters
    }

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

returning to current object

class Person {
    String name;
    int age;

    Person setName(String name) {
        this.name = name;
        return this; // Returns the current object
    }

    Person setAge(int age) {
        this.age = age;
        return this;
    }
}

public class Main {
    public static void main(String[] args) {
        Person person = new Person();
        person.setName("Alice").setAge(25); // Method chaining
    }
}

passing the current object to a method

class Person {
    String name;

    void display(Person person) {
        System.out.println("Person's name: " + person.name);
    }

    void show() {
        display(this); // Passes the current object
    }
}

• usage of this keyword is not allowed in static blocks or methods because they belong to the class rather than the instance.
• improved code readability and prevent errors due to naming conflicts
• it is commonly used in constructors, getters and setters.