Polymorphism in Apex

Polymorphism in Apex

Polymorphism in simple word can be said as One name many forms.

For example , a man can play a role as an Employee, as a Father or as a Husband in his day-to-day life. It means that he can be in any of these form. 

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Polymorphism can be achieved by these two ways :

1. Method Overloading
2. Method Overriding

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Method Overloading

If a class have multiple methods with same name but different parameters (either different length of the arguments or different data types of the arguments), it is known as Method Overloading.

If we have to perform only one operation, with the same name of the methods increases the readability of the program as well as its very logical too.

Let’s suppose if we want to perform addition of the given numbers but there can be any number in arguments as below:

Example of method overloading with different data types of the arguments with same method name like sum.

public class MethodOverloadClass {
    public void sum(Integer no1, Integer no2) {
        System.debug('Sum of 2 Integer is : '+ (no1+no2));
    }
    
    public void sum(Decimal no1, Decimal no2) {        
        System.debug('Sum of 2 Integer is : '+(no1+no2));
    }
}

Execute the below code to see the output

MethodOverloadClass objMethodOverloadClass = new MethodOverloadClass();
objMethodOverloadClass.sum(5,4);
objMethodOverloadClass.sum(5.4,4.2);

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Method Overriding

If a subclass (child class) has the same method as declared in the parent class, it is known as method overriding in Apex.

In other words, we can say If a subclass provides the specific implementation of the method that has been provided by one of its parent class, it is known as method overriding.

Note: Always make sure to achieve method overriding the scope must be of parent and child class relationship and you must have same name method needs to declare into child class with same signature of the method from Parent class to achieve method overriding in Apex.

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Why to use overriding ?

Method overriding is used to provide specific implementation of a method that is already provided by its Parent/Super class. Method overriding is used to achieve runtime polymorphism.

• Why to use overriding ?
• Method name must be same as in the parent class.
• Method name must have same parameter as in the parent class’s method.
• Must be inheritance.

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Example ,

here I have created a parent class and declared it as virtual , so that it can be inherited by child / other class. Also, declared the method as virtual, so that it can be overridden in child class.

public virtual class ParentClass {
  public virtual void show() {
    System.debug('This is Parent-Class');
  }
}

here the Child-Class, override keyword is used to override the method.

public class ChildClass extends ParentClass{
  public override void show(){
    System.debug('This is Child-Class');
  }
}

Execute and see the the output :

ChildClass objChildClass = new ChildClass();
objChildClass.show();
//OR
ParentClass objParentClass = new ChildClass();
objParentClass.display();

Output will be :

This is Child-Class

By : Harshal Lad