Checking if an Object is null at the same time as a value of one of it's fields

Question

Which of these would be correct?

if(dialog != null && dialog.isShowing){}

if(dialog.isShowing && dialog != null){}

if(dialog != null){
   if(dialog.isShowing){}
}

Answer 1

The && operator is called a short circuit operator. This means once the result is known. i.e., false && x is always false it doesn't evaluate the remaining expressions.

A variation on this is using the || short circuit, OR operation, like:

if(text == null || text.isEmpty())