Question

The following for loop prints the numbers 1 to 20 on one line with a space between.

for (int i = 1; i <= 20; i++)
{
System.out.print(i + " " ); // prints each value of i followed by a space on one line
}

Question

Consider the for loop example above. Assume you want to adjust the loop to print only the even values from 1 and 20. What must the loop elements - counter initialization, conditional statement, and counter modification - be set to in order to accomplish the goal.

Review all options listed below carefully. You MUST select 3 answers; one for each element/category:

Counter initialization
Conditional statement
Counter modification
a. int i = 0;
b. int i = 1;
c. int i = 2;
d. i < 20;
e. i <= 20;
f. i > 20;
g. i++;
h. i+=1-;
i. i+=2;

Answer 1

Counter initialization:
`\verb!int i = 2!`.

Conditional statement:
`\verb!i <= 20!`.

Counter modification:
`\verb!i += 2!`.

Explanation:

In the current Java for-loop in this question:

• The counter initialization statement
  `\verb!int i = 1!` in this for-loop would initialize the counter variable to integer
  `1`.
• The conditional statement
  `\verb!i <= 20!` holds as long as the counter is less than or equal to
  `20`. Thus, the largest possible value for the counter would be
  `20\!`.
• The counter modification statement
  `\verb!i++!` is equivalent to
  `\verb!i += 1!`. This statement would add
  `1` to the value of the counter in each iteration.

The even integers between
`1` and
`20` includes
`2,\, 4,\, \dots,\, 20`. It would be necessary to add
`2` each time to get to the next number.

Since the list of even integers starts at
`2`, it would be necessary to initialize the counter variable to
`2\!` rather than
`1`. Thus, replace the counter initialization statement
`\verb!int i = 1!` with
`\verb!int i = 2!`.

The maximum integer that this loop should print is still
`20`. Thus, the conditional statement
`\verb!i <= 20!` does not need to be changed.

The for-loop should add
`2` to the counter each time to get to the next even integer. Thus, the counter modification statement
`\verb!i++!` (or equivalently,
`\verb!i += 1!`) should be replaced with
`\verb!i += 2!`.

Overall, the for-loop should be:

`\begin{aligned}& \verb!for (int i = 2; i <= 20; i += 2) {!\\ &\quad \verb!System.out.print(i +`.