What is the "?:" operator in Java? E.g. sum += digit > 9 ? digit - 9 : digit;

Question

Pretty much what the title says, I have a hard time comprehending this expression, would be grateful if anyone explained the idea behind this expression.

Try grouping the terms in parentheses and see if that makes it clearer. — chrylis -cautiouslyoptimistic-, Jul 19 '18 at 18:03
Which part of the expression confuses you? Would parenthesis help? `sum += (digit > 9 ? digit - 9 : digit);`. Expression uses `>` comparison operator, `-` subtraction operator, `? :` ternary conditional operator, and `+=` additive-assignment operator. Which of these don't you know? — Andreas, Jul 19 '18 at 18:03
In short, it is a way of writing if-statement, just like how you write if-statement in MS Excel. — user3437460, Jul 19 '18 at 18:06
Read about Java Ternary Operators https://alvinalexander.com/java/edu/pj/pj010018 — Benjamin RD, Jul 19 '18 at 18:09

score 6 · Answer 1 · answered Jul 19 '18 at 18:04

6

This is ternary operation it is the same as a if else in one expression;

The statement: sum += digit > 9 ? digit - 9 : digit;

Is the same as:

if (digit > 9)
  sum += digit - 9;
else
  sum += digit;

answered Jul 19 '18 at 18:04

Marcos Vasconcelos

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score 0 · Answer 2 · edited Jul 19 '18 at 18:07

0

It is a Java Ternary Operator

Basically if the Sum + digit is greater than 9 than sum will equal digit-9 OR if not it will just equal digit

So this is same as

if (digit > 9)
  sum += digit - 9;
else
  sum += digi

edited Jul 19 '18 at 18:07

Kartik Shandilya

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answered Jul 19 '18 at 18:03

marshall legend

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Not quite. If digit > then `sum = sum + digit -9` else `sum = sum + digit` – scrappedcola Jul 19 '18 at 18:07
Oh yes, you're correct. I forgot to account for the `+=` operation. Thank you @scrappedcola for catching my mistake and correcting it. – marshall legend Jul 19 '18 at 18:09

What is the "?:" operator in Java? E.g. sum += digit > 9 ? digit - 9 : digit;

2 Answers2