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I have a base class with age and name as instance members and derived class with bonus. I am overriding equals in Derived class. I know how equals works in Java when there is a single base class. But I am not able to understand how it works in case of inheritance. I want to check if two derived objects are equal.
I was expecting the output to be
This class = Base, Other class = Derived
instead the output is
This class = Derived, Other class = Derived
What is super in equals method of derived class exactly doing?Isnt it referring to Base?
public class Base{
private int age;
private String name;
public Base(int age, String name){
this.age = age;
this.name = name;
public int getAge(){
return age;
public String getName(){
return name;
@Override
public boolean equals(Object otherBase){
//Check if both the references refer to same object
if(this == otherBase){
return true;
if(otherBase == null){
return false;
System.out.println("This class ="+this.getClass().getCanonicalName()+", Other class = "+otherBase.getClass().getCanonicalName());
if(this.getClass() != otherBase.getClass()){
return false;
if(! (otherBase instanceof Base)){
return false;
Base other = (Base) otherBase;
return this.age == other.age && this.name.equals(other.name);
public static void main(String[] args){
Derived d1 = new Derived(10,6,"shri");
Derived d2 = new Derived(10,5, "shri");
if(d1.equals(d2)){
System.out.println("Equal");
}else{
System.out.println("Not Equal");
class Derived extends Base{
private int bonus;
public int getBonus(){
return bonus;
public Derived(int bonus, int age, String name){
super(age, name);
this.bonus = bonus;
@Override
public boolean equals(Object otherDerived){
if(!(super.equals(otherDerived))){
return false;
Derived derived = (Derived) otherDerived;
return bonus == derived.bonus;
–
delegate the comparison of the
age
and
name
to the
Base
class
if it is not the same, return false
otherwise compare the value of the
bonus
field in the
Derived
class
The call of
super.equals()
will call the
equals()
from super class (
Base
), but
this
still represents the real instance, e.g.
Derived
in your case.
–
super
is used to call the
overriden
equals method (the one defined in
Base
). More generally,
super
references the superclass of the type in which it is used, so in this case yes it refers to
Base
. However, the referenced object's type
at runtime
is still
Derived
.
In the
Base#equals()
method, the expression
this.getClass().getCanonicalName()
returns the name of the class for the object at runtime. Even if the expression is called in the
equals
method of the base class, the actual type is
Derived
. This is what the
getClass
method does as mentioned in the Javadocs:
Returns the
runtime
class of this Object.
If you ever need to get the name of the superclass, you can use
this.getClass().getSuperclass().getCanonicalName()
.
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