AP Computer Science Exam Question

Consider the following method declaration in Java:

public class MathUtils {
    public static int multiply(int a, int b) {
        return a * b;
    }
}

1. Explain the purpose of the public keyword in the method declaration.
2. Explain the purpose of the static keyword in the method declaration.
3. Write code to invoke the multiply method in the MathUtils class with the values 5 and 3. Store the result in a variable called product.
4. Explain the steps involved in the method invocation process.
5. What would be the value of product after the invocation?

Answer:

1. The public keyword in the method declaration allows the method to be accessible from anywhere in the program. This means that other classes in different packages can access and use this method.

2. The static keyword in the method declaration makes the method belong to the class itself rather than to an instance of the class. This means that the method can be called using the class name (MathUtils.multiply()) instead of creating an object of the class.

3. To invoke the multiply method in the MathUtils class with the values 5 and 3, you can use the following code:

int product = MathUtils.multiply(5, 3);

4. The steps involved in the method invocation process are as follows:

   • The code invokes the method by using the class name followed by the dot operator (MathUtils.multiply()).
   • The arguments (5, 3) are passed to the method.
   • The method is executed.
   • The result of the multiplication is returned.

5. The value of product after the invocation would be 15, as the multiply method multiplies 5 and 3.