`This` Keyword

General

this keyword is used as a reference to the object itself
- It can be used to reference the object’s instance variables, methods, constructors, etc.
- Enables instance variables to access an object’s variables and methods
It is used to avoid confusion between instance variables and parameter values

public class F {
    private int i = 5;
    public void setI(int i) {
    this.i = i; //this.i refers to the instance variable i
    // i refers to the parameter i
    }
}

Calling Another Constructor

this keyword can be used to invoke another constructor of the same class

Format: this.(argument)

public class Circle {
    private double radius;
    public Circle(double radius) {
        this.radius = radius; //this keyword references the hidden data field, radius
    }
    public Circle() {
        this(1.0); //passes 1.0 as an argument to the 1st constructor
    }
}

Calling Other Methods

this keyword can be used to call other methods in the same class

Format: this.methodName()

public class Robot {
    private String name;

    public Robot(String name) {
        this.name = name;
    }

    public void start() {
        System.out.println(this.name + " is starting up...");
        this.speak();  // Calls the speak method of the current object
    }

    public void speak() {
        System.out.println(this.name + " says: 'Hello, human!'");
    }
}

Popcorn Hacks

public class Minion {
    private String eyeCount;
    private int height;

    public minion(String eyeCount, int height) {
        this.eyeCount = eyeCount;
        this.height = height;
    }

    public void setHeight(int height) {
        this.height = height;  
    }

    public String getEyeCount() {
        return this.eyeCount;  
    }

    public boolean isTallerThan(Minion otherMinion) {
        return this.height > otherMinion.height;  
    }

    public static void main(String[] args) {
        Minion minion1 = new Minion(1, 28);
        Minion minion2 = new Minion(2, 43);

        System.out.println("minion 1 number of eyes: " + minion1.getEyeCount());
        System.out.println("Is minion1 taller than minion2? " + minion1.isTallerThan(minion2));

        minion2.setHeight(50);
        System.out.println("Is minion1 still taller than minion2? " + minion1.isTallerThan(minion2));
    }
}

What is the output of the statement System.out.println(“minion 1 eyeCount: “ + minion1.getEyeCount());? Explain why the this keyword is useful in the getEyeCount() method.
What does the isTallerThan() method compare? How does the this keyword play a role in this comparison?
What happens to the result of System.out.println(“Is minion1 taller than minion2? “ + minion1.isTallerThan(minion2)); after minion2.setHeight(50); is called? Why does the result change?
Do minion1 and minion2 refer to the same object in memory?

This Keyword

General

Calling Another Constructor

Calling Other Methods

Popcorn Hacks

`This` Keyword