What is this in the following program in setter block....?

Question

public class Vehicle {
private String color;

// Getter
public String getColor() {
return color;
}

// Setter
public void setColor(String c) {
this.color = c;
}
}

class Program {
public static void main(String[ ] args) {
Vehicle v1 = new Vehicle();
v1.setColor("Red");
System.out.println(v1.getColor());
}
}

Answer 1

this is a reference to the object itself. You only need to use this if the class variable is the same as the setter parameter, like so:
public void setColor(String color) {
this.color = color;
}

this differentiates between the class variable and the method argument