'Why do we use Static keyword for initializing a variable

I'm an absolute beginner. I have a question regarding this recursive program which prints Fibonacci series.

My question is: why they used static keyword to declare the integer variable n1, n2 and n3 in the 2nd line of code ?

Also why they use static void for the recursive function printFibonacci(int count) in the 3rd line of code?


class FibonacciExample2{
 static int n1=0,n2=1,n3=0; 
 static void printFibonacci(int count)
{

if(count>0){

n3 = n1 + n2;

n1 = n2;

n2 = n3;

System.out.print(" "+n3); printFibonacci(count-1);

}

}

public static void main(String args[]){

int count=10;

System.out.print(n1+" "+n2);//printing 0 and 1 printFibonacci (count-2);

}

}
javastaticfibonacci


Solution 1:[1]

Static members are present in all the instantiated objects. You can see static members as members shared by all objects of a certain class. You should be careful when modifying a static member as this member will be modified in all objects. Static methods are methods that can be called without an object. In your case FibonacciClass.method(). However in static methods only static members can be used as these are not dependent upon an object.

Solution 2:[2]

The function for the Fibonacci series is here

So you don't need to create static fields for it

int fibonacci(int x){
if (x <= 1){
  return x;
}
return fibonacci(x-2) + fibonacci(x-1);

}

it works like this if you provide 5

       fibonacci(3)           +                     fibonacci(4)
fibonacci(1) + fibonacci(2)             fibonacci(2) +              fibonacci(2)
              /    \                     /       \                      /  \
    fibonacci(1) + fibonacci(1)  fibonacci(1) + fibonacci(1) fibonacci(1) + fibonacci(1)

add all ones and the answer will be returned. check how methods are working in stack memory to Cleary understand this.

Solution 3:[3]

In this exact case, I suppose they've used the static word since they want to use the method(printFibonacci) and the fields(n1, n2, n3) directly in the main method(which java requires to be static). Static methods can access only static data members. I suppose you already know that there are two types of members- static and dynamic(instance). The static belong to the class itself, whereas the dynamic ones belong to individual instances of this class. Therefore, if you want to use a dynamic member(field, method, etc.) of a class, you would be forced to make an instance of this class. So, if they had declared the n1,n2,n3 and the printFibonacci method to be non-static, they would be forced to make an instance of the FibonacciExample2 class and access them through that instance, which is utterly pointless and verbose.

Sources

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Source: Stack Overflow

Solution Source
Solution 1 AlexAlbu
Solution 2 Zabith Mohammed
Solution 3

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