How to create factorial program in dart language

//Create main() function of dart

 void main(){

Factorial factorial=Factorial();

print("Is factorial:"+ factorial.factorial(4).toString());

}

//output

Result=> factorial:24

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//create a class of factorial 

class Factorial{

//this is a method of factorial

  factorial(int n){

    if(n==0 || n==1){

      return 1;

    }else{

      return n*factorial(n-1);

    }

  }

}