Question:

Consider the following Java code:

public class VariableScopeExample {
    
    public static void main(String[] args) {
        int numA = 5;
        int numB = 10;
        int numC = 15;
        
        performCalculation(numA, numB);
        performCalculation(numA, numC);
        performCalculation(numB, numC);
        
        System.out.println(numA + ", " + numB + ", " + numC);
    }

    public static void performCalculation(int a, int b) {
        int result = a + b;
        a = result * 2;
        b = result * 3;
        System.out.println("a = " + a + ", b = " + b);
    }
}

Examine the given code and evaluate the output that will be produced when it is executed. Explain the scope and lifetime of the variables numA, numB, numC, a, b, and result and how their values are affected by the method performCalculation. Provide a step-by-step explanation of the entire process.

Answer:

The output that will be produced when the given code is executed is:

a = 30, b = 45
a = 40, b = 60
a = 30, b = 45
5, 10, 15

Explanation:

1. In the main method, three integer variables numA, numB, and numC are declared and initialized with values 5, 10, and 15, respectively.

2. The first call to the performCalculation method is made with the parameters numA and numB (values 5 and 10). Within the method:

   • A new local variable a is created and assigned the value of numA (5) and a new local variable b is created and assigned the value of numB (10).
   • Another local variable result is created and assigned the sum of a and b i.e., 15.
   • The value of a is updated to result * 2 which is 30.
   • The value of b is updated to result * 3 which is 45.
   • The output "a = 30, b = 45" is printed.

3. The second call to the performCalculation method is made with the parameters numA and numC (values 5 and 15). Within the method:

   • New local variables a and b are created and assigned the values of numA (5) and numC (15) respectively.
   • Another local variable result is created and assigned the sum of a and b i.e., 20.
   • The value of a is updated to result * 2 which is 40.
   • The value of b is updated to result * 3 which is 60.
   • The output "a = 40, b = 60" is printed.

4. The third call to the performCalculation method is made with the parameters numB and numC (values 10 and 15). Within the method:

   • New local variables a and b are created and assigned the values of numB (10) and numC (15) respectively.
   • Another local variable result is created and assigned the sum of a and b i.e., 25.
   • The value of a is updated to result * 2 which is 50.
   • The value of b is updated to result * 3 which is 75.
   • The output "a = 30, b = 45" is printed.

5. Finally, after all method calls, the values of numA, numB, and numC remain unchanged and are printed using println in the main method. Thus, the output is "5, 10, 15".

Scope and Lifetime of Variables:

• numA, numB, and numC are declared as instance variables within the main method and their scope is limited to that method. Their lifetime is until the main method execution is complete.
• a, b, and result are declared as local variables within the performCalculation method and their scope is limited to that method. They are created and destroyed every time the method is called.