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When a developer uses an identifier that has the same name as a public class, such as {{Vector}}, a subsequent maintainer might not be awareunaware that this identifier does not actually refer to {{java.util.Vector}}, and might unintentionally use the custom {{Vector}} insteadrather ofthan the original {{java.util.Vector}} class. The custom type {{Vector}} can [shadow|BB. Definitions#shadow] a class name from {{java.util.Vector}}, as specified by the JLS, [§6.3.2, "Obscured Declarations"|http://java.sun.com/docs/books/jls/third_edition/html/names.html#6.3.2] of the _Java Language Specification_ \[[JLS 2005|AA. Bibliography#JLS 05]\]. This can result in unexpected program behavior.

Well-defined import statements can resolve these issues. However, when reused name definitions are imported from other packages, use of the _type-import-on-demand declaration_ (see the JLS, [§7.5.2, "Type-Import-on-Demand Declaration"|http://java.sun.com/docs/books/jls/third_edition/html/packages.html#7.5.2] of the _Java Language Specification_ \[[JLS 2005|AA. Bibliography#JLS 05]\]) can complicate a programmer's attempt to determine which specific definition was intended to be used. Additionally, a common, and potentially misleading, tendency practice that can lead to errors is to produce the import statements _after_ writing the code, often via automatic inclusion of import statements by an IDE. This creates further ambiguity with respect to the names;. whenWhen a custom type is found earlier than the intended type in the Java include path than the intended type, no further searches are conducted. Consequently, the wrong type is silently adopted. 

When the developer and organization control the original shadowed class, it may be preferable to change the design strategy of the original in accordance with Bloch's _Effective Java_ \[[Bloch 2008|AA. Bibliography#Bloch 08]\], "Item 16:, Prefer interfaces to abstract classes." Changing the original class into an interface would permit class {{MyVector}} to declare that it implements the hypothetical {{Vector}} interface. This would permit client code that intended to use {{MyVector}} to remain compatible with code that uses the original implementation of {{Vector}}.