Short-circuit OR

Perhaps you noticed that to answer the question you only needed to evaluate the first subexpression:

12 > 6 || 18 > 1
------ 
true

Once you know that this subexpression is true there is no need to go further. true OR anything is true.

The || OR operator is also a short-circuit operator. Since OR evaluates to true when one or both of its operands are true, short-circuit evaluation stops with the first true.

The OR operator comes in a non-short-circuit version as well: | (this is a single vertical bar.) When this operator is used, both operands are evaluated no matter what the outcome of the first operand. The short-circuit OR works like this:

To evaluate X||Y, first evaluate X. If X is true then stop: the whole expression is true. Otherwise evaluate Y and OR the two values.

As with the short-circuit AND, be careful when using methods that have side effects. If you are depending on a method's side effect, be sure that the method executes.