Java String hashCode of null string

Question

Only interesting, why method hashCode() in java.lang.String is not static? And in case of null return e.g. -1 ? Because frequently need do somethihg like:

String s;
.............
if (s==null) {
  return 0;}
else {
  return s.hashCode();
}

Thanks.

Answer 1

As others have noted hashCode is a method on Object and is non-static because it inherently relies (i.e. belongs to) an object/instance.

Note that Java 7 introduced the Objects class, which has the hashCode(Object) method, which does exactly what you want: return o.hashCode() if o is non-null or 0 otherwise.

This class also has other methods that deal with possibly-null values, such as equals(Object, Object), toString(Object) and a few others.