Quiz 2

Quiz 2: I/O & Methods

Question 1

Consider the following statement in Java:

Scanner in = new Scanner(System.in)

For each of the following, check True (T) or False (F).

Question	T	F
The variable ‘in’ is of type ‘Scanner’
The ‘in’ in ‘System.in’ on the righthand side is the same entity as the variable ‘in’ on the lefthand side.
‘new’ tells Java to import the Scanner class
‘System.in’ is a method in ‘Scanner’

Answer

| Question | T | F | | ----- | ---- | ---- | | The variable 'in' is of type 'Scanner' | x | | | The 'in' in 'System.in' on the righthand side is the same entity as the variable 'in' on the lefthand side. | | x | | 'new' tells Java to import the Scanner class | | x | | 'System.in' is a method in 'Scanner' | | x | 'in' on the lefthand side is a variable of type 'Scanner'. 'in' as part of 'System.in' on the righthand side is a method in System. 'new' tells Java to _create a new instance_ of the Scanner class. The statement 'import java.util.Scanner;' at the top of the file would tell Java to _import_ the Scanner class. 'System.in' is a method call to the 'in' method in 'System'. It is an argument passed to 'Scanner()'. It is not a method in Scanner.

Question 2

Consider the following small program in Java.

class Question {
    public static void showAdd(int a, double b) {
        double x = a + b;
        System.out.println(x);
    }
    public static void main(String args[]) {
        int i = 5;
        double j = 0.4;
        showAdd(i, j);
    }
}

A: What are the parameters of the ‘showAdd()’ method?

Answer

'int a' and 'double b'

B: What are the arguments passed to the ‘showAdd()’ method?

Answer

i (which is 5) and j (which is 0.4) There are many ways to answer this part of the question; the important thing is to understand that i and j are the arguments being passed, and that 'int a' and 'double b' are the parameters being assigned.

Question 3

In a sentence or two, explain the difference between what a method returns and what a method prints.

Answer

A return means that the entire method, when evaluated, will be converted into whatever the return value is. You can save the value that a method returns as a variable, or use it directly. A print statement in a method will simply print whatever is asked when the execution of the code reaches that line.