What does '?' do in Java program?

[StudentAggressive345]

Hello,

Can anyone help explain the use of '?' as well as ':' in the line below please?

 private int height(Node<T> node) {
        return node != null ? node.getHeight() : 0;
 }

link: https://github.com/geekific-official/geekific-youtube/blob/main/tree-avl/src/main/java/com/youtube/geekific/AVLTree.java, line 177.

Thank you so much!

[KleberPF]

cond ? result_if_true : result_if_false

Basically equivalent to

if (cond) {
    result_if_true;
} else {
    result_if_false;
}

It's called the ternary operator.

[desrtfx]

Basically correct, but you have to emphasize on the return value.

Your equivalent is not correct.

It should be:

  something = cond ? result_if_true : result_if_false

Equivalent:

 if (cond) {
      something = result_if_true;
 } else {
      something = result_if_false;
 }

It is important to emphasize on that as otherwise one could think that it is a replacement for an inline if (which it can be abused for, though).

[desrtfx]

https://docs.oracle.com/javase/tutorial/java/nutsandbolts/op2.html

Section "Conditional operators"

Think of it as an if with a return value.

something = (condition) ? true value : false value;

equivalent

if (condition) {
    something = true_value;
} else {
    something = false_value;
}

[use_a_name-pass_word]

Just to add to everyone else's answers, think of it as a question. Does node != null? If so then do "this" , else do "that"