Question

In the following:

for (String deviceNetwork : deviceOrganizer.getNetworkTypes(deviceManufacturer)) {
    // do something
}

Is it safe to assume that deviceOrganizer.getNetworkTypes(deviceManufacturer) will be called only once?

Answer 1

Yes, absolutely.

From section 14.14.2 of the spec:

If the type of Expression is a subtype of Iterable, then let I be the type of the
expression Expression.iterator(). The enhanced for statement is equivalent to a basic for
statement of the form:

for (I #i = Expression.iterator(); #i.hasNext(); ) {
        VariableModifiersopt Type Identifier = #i.next();
   Statement
}

(The alternative deals with arrays.)

Note how Expression is only mentioned in the first part of the for loop expression – so it’s only evaluated once.