For maximum reusability, methods should accept parameters with as little specialization as possible. So unless specific features from a child class are required by a method, a type higher up the class hierarchy should be used instead.
public void printSize(ArrayList<Object> list) { // Collection can be used instead System.out.println(list.size()); } public static void loop(List<Object> list) { // java.lang.Iterable can be used instead for (Object o : list) { o.toString(); } }
public void printSize(Collection<?> list) { // Collection can be used instead System.out.println(list.size()); } public static void loop(Iterable<?> list) { // java.lang.Iterable can be used instead for (Object o : list) { o.toString(); } }
Parameters in non-public methods are not checked, because such methods are not intended to be generally reusable. java.lang.String
parameters are excluded, because String is immutable and can not be always substituted for more generic type. Parameters used in any other context
than method invocation or enhanced for loop are also excluded.