Page History

This noncompliant code example shows how the programmer can confuse overloading with overriding. At compile time, the type of the object array is {{List}}. The expected output is {{ArrayList}}, {{LinkedList}} and {{List is not recognized}} ({{java.util.Vector}} does not inherit from {{java.util.List}}). However, in all three instances {{List is not recognized}} is displayed. This happens because in overloading, the method invocations are not affected by the runtime types but only the compile time type ({{List}}). It is dangerous to implement overloading to tally with overriding, more so, because the latter is characterized by inheritance unlike the former. \[[Bloch 082008|AA. Java References#Bloch 08]\]

This compliant solution uses a single {{display}} method and {{instanceof}} to distinguish between different types. As expected, the output is {{ArrayList, LinkedList, List is not recognized}}. As a general rule, do not introduce ambiguity while overloading so that the code is clean and easy to understand. \[[Bloch 082008|AA. Java References#Bloch 08]\]

\[[API 062006|AA. Java References#API 06]\] [Interface Collection|http://java.sun.com/j2se/1.4.2/docs/api/java/util/Collection.html]
\[[Bloch 082008|AA. Java References#Bloch 08]\] Item 41: Use overloading judiciously