Puzzle 1 - It's Elementary

OK, so the last puzzle was a bit tricky, but it was about division. Everyone knows that division is tough. This program involves only addition. What does it print?


public class Elementary {

public static void main(String[] args) {

System.out.println(12345 + 5432l);

}

}




Solution 4: It's Elementary
On the face of it, this looks like an easy puzzle—so easy that you can solve it without pencil or paper. The digits of the left operand of the plus operator ascend from 1 to 5, and the digits of the right operand descend. Therefore, the sums of corresponding digits remain constant, and the program must surely print 66666. There is only one problem with this analysis: When you run the program, it prints 17777. Could it be that Java has an aversion to printing such a beastly number? Somehow this doesn't seem like a plausible explanation.

Things are seldom what they seem. Take this program, for instance. It doesn't say what you think it does. Take a careful look at the two operands of the + operator. We are adding the int value 12345 to the long value 5432l. Note the subtle difference in shape between the digit 1 at the beginning of the left operand and the lowercase letter el at the end of the right operand. The digit 1 has an acute angle between the horizontal stroke, or arm, and the vertical stroke, or stem. The lowercase letter el, by contrast, has a right angle between the arm and the stem.

Before you cry "foul," note that this issue has caused real confusion. Also note that the puzzle's title contained a hint: It's El-ementary; get it? Finally, note that there is a real lesson here. Always use a capital el (L) in long literals, never a lowercase el (l). This completely eliminates the source of confusion on which the puzzle relies:

System.out.println(12345 + 5432L);


Similarly, avoid using a lone el (l) as a variable name. It is difficult to tell by looking at this code snippet whether it prints the list l or the number 1:


// Bad code - uses el (l) as a variable name

List<String> l = new ArrayList<String>();

l.add("Foo");

System.out.println(1);




In summary, the lowercase letter el and the digit 1 are nearly identical in most typewriter fonts. To avoid confusing the readers of your program, never use a lowercase el to terminate a long literal or as a variable name. Java inherited much from the C programming language, including its syntax for long literals. It was probably a mistake to allow long literals to be written with a lowercase el.