Question

Part 1

Describe (in words, not code) a programming scenario where the post-fix and the pre-fix operators impact the value of a variable. Using the same scenario, the value of the variable is different when using the post-fix operation versus the pre-fix operation.

Part 2

Explain static vs non-static methods. Why do we need the keyword static for some methods and not for others?

Answer 1

Answer:

Part 1:

In programming, prefix operator is used before the variable ( e.g.,++value or --value ) and postfix operator is used after the variable (e.g., value++ or value--).

The use of prefix or postfix operators impact the value of a particular variable very differently in terms of both increment and decrement operators.

In the prefix version (i.e., ++value or --value ), first, the value is incremented/decremented, and then the new value is returned.

In the postfix version (i.e., value++ or value--), the original value is returned first and then the value is incremented/decremented.

For Example, let us see the following code snippet:

int i = 5;

int j = ++i;

cout<<j;

int k = i++;

cout<<i;

a.) Initially, i is set to 5

b.) In the next line, i is incremented to 6 and the new value of i is copied into j and then printed in the next line. So now j is equal to 6.

c.) On the 4th line, i is incremented to 7. The original value of i which is 6 is copied into k. So k is now equal to 6.

But when in the next line we print i, the value shows 7 but j and k will be 6

The same thing happens for postfix and prefix versions of --

Part 2:

A static method belongs to the class, and we do not have to create an instance of the class to access the static method .To create a static method we use the keyword static in front of the method name. A static method can call only other static methods, it cannot call a non-static method. Also, a static can only access static variables, it cannot access instance variables.

On the other hand, a non-static method belongs to an object of the class, and we have to create an instance of the class to access the non-static method. A non-static method can access any static method without creating an instance of the class. A non-static method can access any static variable without creating an instance of the class because the static variable belongs to the class

E.g., static methods:

class Calc {

static int product(int x, int y) { //static method

   return x * y;

}

public static void main(String[] args) {

   int ans = Calc.product(5, 3); //method is called directly without creating an instance first

System.out.println(ans); }

}

non-static methods:

class Calc {

int product(int x, int y) { //non static method

   return x * y;

}

public static void main(String[] args) {

   Calc calcnew = new Calc();

   // we have to first create an instance of the class Calc to call the non-static method

   int ans = calcnew.product(5, 3); // call the non-static method

   System.out.println(ans);

}

}

The main reason some methods are declared static because of convenience

If we do not make our method/function and variable static, we cannot access that without creating a Object.

But, if we make them static, we do not have to create an object to access that method.