this and super keywords

1 Learn

this refers to the current object. It is often used when a parameter has the same name as a field: this.name = name.

super refers to the parent class. super(...) calls the parent constructor (as the first statement), and super.method() calls the parent's version of a method.

Want more detail? Open the full lesson

2 See the Code

Java

class Person {
    String name;
    Person(String name) {
        this.name = name;
    }
    void intro() { System.out.println("I am " + name); }
}

class Teacher extends Person {
    String subject;
    Teacher(String name, String subject) {
        super(name);
        this.subject = subject;
    }
    @Override
    void intro() {
        super.intro();
        System.out.println("I teach " + subject);
    }
}

public class School {
    public static void main(String[] args) {
        new Teacher("Mr. Rao", "Java").intro();
    }
}

this.name = name — the field gets the parameter's value.
super(name) runs Person's constructor first.
super.intro() reuses the parent's method, then adds more.

Output

I am Mr. Rao
I teach Java

3 Practice

Create Employee(name) and Manager(name, team) that uses super(name) and this.team = team.

Try it in your own Java setup or write it in the Practice Notebook.

4 Quick Check

1. this refers to...
2. Where must super(...) appear in a constructor?

Step 5

Answer and check the Quick Check above to unlock this.

Day 22