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Inheritance In Java

Saptarshiok

6 min readMar 15, 2025

Inheritance.

The idea is to adopt or inherit the properties (functions , variable , constants also constructor )

Of a particular class to another class;

The class which is adopting the properties of another class is said to be the child class ;

The class which will be inherited by another class can be called as the parent class;

This parent and child class comes from real world examples like : a mother is good at drawing and good at singing :- so their child can inherit both of her qualities and also can have his/her own quality such as the child can be good at sports too.

The exact same way inheritance works the same in java .

Let’s make an outlook of this inheritance .

Single level inheritance .

Parent class:-

Child class:-

Test class ➖

We can see that the parent class has the properties such as eats , sleeps, has a name and a age .

But the child class does not have one but still it can access the parents class properties by inheriting it with the help of extends keyword.

Multilevel Inheritance :-

This idea is same as the parent and child relation , only we can imagine more that the child has a grandparent

, so the child now can adopt the properties of both parent and grandparent .

Example:-

The topmost parent class :-

The next parent class :-

The lowermost child class :-

The test class :

In this code parent class extends grandparent class and child class extends parents class .

So both the parents and child class do have the properties of the grandparent class.

Now we can see in the above code that grandparents also have a property of snoring .

But children usually does not snore .

So we can also redefine the property (here function)

In the child class.

Example :- Grandparent class

Child class :-

Test class :-

Output

Here we can see for the child snors function return false and for grandparent is true ,

Because we have redefined the snores function in child for the child class ,

This redefining of the same function in the child class as the parent class for different purposes is known as function overriding .

As the child class already has a snors function it wont call the parents snors function.

How does constructors works in inheritance :-

The constructors are for the purpose of initialising the initial parameters .

Thus in inheritance first the parent’s constructor is called then the child’s constructor is called on creating a child class object .

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Example

Now on creating a object of a class :-

Output:

This is how constructors are called in inherited classes , but it does not mean that the child class cannot have a different constructor from parent class:

Now the child class also have a different constructor of its own :

Calling the parameterized child constructor:

Output:

Here although the constructor is not similar to the parent class, the parent class constructor will be called before the child’s constructor.

Some points :

No static functions can be accessed by any child class .
Static functions can only be used within the class .
Child class also cannot access private properties of the parent class.

super Keyword:

This is a keyword that refers to the parent class.

In every constructor call in child class the reason it first executes the parent class constructor because there is a default super keyword written in the beginning of every constructor.

For example;

This super(); keyword is already present by default in the beginning of every class constructor .

This is responsible for calling the parent class constructor if there is any parent of that class.

Super keyword cannot be written in the end of any constructor as it does not maintain the logic of calling the parent constructor first .

For example:

If we try to forcefully write a super keyword in the end of any constructor an error will occur .

But this super keyword is not for only calling constructors of parent classes. It gives reference to the parent class , thus it can be used to call functions of the parent class even after function overriding .

Parent class :

Child class :

Test class :

Output:

In this code even if there is a function overriding and normally the parent function snors() won’t be called , but explicitly using the super key word after the function overriding still the parent snors() class will be called .

Now it is understood that we can do single inheritance and multilevel inheritance .

But in java we cannot do multiple inheritance ,

Meaning we can’t inherit more than one class .

For example: