Public Object: Java Minutiae

Java Minutiae - I love ternary

I love the ? : ternary operator. It makes my code feel tighter. Plus, I get to save code - fewer assignments, fewer return statements, and variable declarations are inline. In the code I was writing yesterday, a duplicated call to 'add()' made me itch for the ternary:

    for (String key : keys) {
      if (getCardinality(key) == 1) {
        singleValuedKeys.add(key);
      } else {
        multiValuedKeys.add(key);
      }
    }

Unfortunately, with standard use of a ternary, the code gets bigger instead of smaller:

    for (String key : keys) {
      Set<String> setToAddTo = (getCardinality(key) == 1)
          ? singleValuedKeys
          : multiValuedKeys;
      setToAddTo.add(key);
    }

Taking it one-step further, I inline the setToAddTo variable. This is where the code loses its familiar feel:

    for (String key : keys) {
      ((getCardinality(key) == 1)
          ? singleValuedKeys
          : multiValuedKeys).add(key);
    }

It's tight, but somehow I've written Java code that doesn't have the Java feel. So I ended up dropping the ternary, and went with the familiar if/else structure. What's your preference?

# posted by Jesse Wilson on Monday, March 10, 2008

I love ternary, too, but I'd go w/ A or B.

# posted by Bob on March 10, 2008 2:52 PM

I find readability suffers with all but the most trivial uses of ?:. I don't use it unless I can get it on one line, which is rarely given Java's love of trulyGignormousIdentifiers.

Scala's if *expression*, on the other hand, that I like.

x = if (test) { trueval }
else { falseval }

(In scala blocks are expressions returning the value of their last component expression.)

# posted by Benjamin on March 10, 2008 2:55 PM

Your variable naming keeps the 3rd choice readable. I'd go for it. Sometimes it's good to write provocative code, just to see what happens. It can inspire weirdness in the people around you.

# posted by matthew on March 10, 2008 3:19 PM

I love ternary and use it all the time, but might not in your case. Usually I find it not as clear if it's the message receiver that's being determined by the ternary (like what you had). But when it's a parameter:

foo.bar(blah ? 0 : 1)

or an assignment:

foo = bar ? 0 : 1

then I think it's quite readable.

# posted by lowellk on March 10, 2008 5:09 PM

I like B. For some reason the second statement is an "obvious place to stick a break point". And, I'd just stick things on one line. The setToAddTo name tells me "hey we're deciding upon a set"; I really don't need the rest of the linebreaks to help me scan.

But we are deciding upon a rule based on cardinality of the key. 'setMatchingKeyCardinality' is long, but more descriptive than 'setToAddTo'.

# posted by Tristan on March 11, 2008 3:05 AM

I come down on the side of C being difficult to read. Maybe that's because I don't love ternary! I don't write it myself, so when I read it, I find myself saying out loud "if...then...else". So, if you are working with mortal coders like me, consider keeping it simple.

# posted by Frank on March 13, 2008 12:09 PM

For readability, if-else wins hands down.

# posted by Bharath on March 19, 2008 10:39 AM

Barath, I disagree. if/else often requires separation of variable declaration from assignment:

for (String key : keys) {
__Set<String> setToAddTo;
__if (getCardinality(key) == 1) {
____setToAddTo = singleValuedKeys;
__} else {
____setToAddTo = multiValuedKeys;
__}
__setToAddTo.add(key);
}

Only the ternary lets me combine declaration and assignment without duplicating the call to Set#add.

# posted by swankjesse on March 19, 2008 7:44 PM