Description Chris Long 2005-12-01 12:19:33 EST

This is a minor point, but on the "Basic Techniques" page in the Programming Guide
(http://www.eclipse.org/aspectj/doc/released/progguide/examples-basic.html), in the section "The HashablePoint aspect", it says

"Different implementations [of hashCode] are allowed [to] return different integers, but must return distinct integers for distinct objects, and the same integer for objects that test equal."

It is not true that hashCode must return distinct integers for distinct objects. It's preferable, since it makes the hashCode more useful (and may speed up hashtables, etc.), but it's not required. From the javadocs on Object.hashCode:

"It is not required that if two objects are unequal according to the equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hashtables."

BTW, I didn't specify a version because I couldn't find a version number in the document.