If an else statement is used and the expression evaluates to false, then the code following the else will be performed. If the else is not used, then none of the code associated with the if statement will execute.
I thought single if statements do work properly in Java. Am I wrong or does every if statment require an else attached with it?
Actually, the quote is quite correct. It is your understanding of it that may be flawed. Nowhere does it state that else is required, in fact it specifically mentions what happens when there is no else clause provided.
You may have been confused by the wording "none of the code associated with the if statement will execute. " but remember that this is related to the first part of the statement which says "If an else statement is used and the expression evaluates to false" which indicates that the entire statement explains only the flow of program logic in the case that the logical expression in the if statement returns false. If that is the case then indeed the code inside the conditional expression is not executed and optional code contained inside an else clause will be evaluated in its stead.
