Question:

A Math class has a method called multiplyByTwo that takes an integer as input and returns the result of multiplying the input by 2. The method is defined as follows:

public static int multiplyByTwo(int num) {
    return num * 2;
}

Which of the following is the correct way to call and print the result of the multiplyByTwo method with an input of 5?

A) multiplyByTwo(5);

B) System.out.print(multiplyByTwo(5));

C) System.out.print(multiplyByTwo(5).toString());

D) System.out.println(multiplyByTwo(5));

Explain your answer choice.

Answer:

The correct answer is D) System.out.println(multiplyByTwo(5));.

The multiplyByTwo method returns an integer value, so in order to see the result, we need to print it to the console.

Option A (multiplyByTwo(5);) only calls the method but does not print or store the result, so the output will not be visible.

Option B (System.out.print(multiplyByTwo(5));) calls the method and prints the result using System.out.print, which displays the result without a new line character. However, the question specifies to print the result, so this option does not fully satisfy the requirement.

Option C (System.out.print(multiplyByTwo(5).toString());) also calls the method and attempts to print the result using System.out.print. However, since the method returns an int which is a primitive data type, it does not have a toString method. Therefore, this option will result in a compilation error.

Option D (System.out.println(multiplyByTwo(5));) calls the method and prints the result using System.out.println. The println method prints the result followed by a new line character, which aligns with the requirement of printing the result. Hence, this is the correct way to call and print the result of the multiplyByTwo method with an input of 5.