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Well-defined import statements can resolve these issues. However, when reused name definitions are imported from other packages, use the _type-import-on-demand declaration_ (see [&#xA7;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_ \[[JLS 2005|AA. Bibliography#JLS 05]\]). Additionally, a common, and potentially misleading, tendency 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; when a custom type is found earlier in the Java include path than the intended type, no further searches are conducted.

Noncompliant Code Example (Class Name)

This noncompliant code example implements a class that reuses the name of the class java.util.Vector. It attempts to introduce a different condition for the isEmpty() method for interfacing with native legacy code by overriding the corresponding method in java.util.Vector. Unexpected behavior can arise if a maintainer confuses the isEmpty() method with java.util.Vector.isEmpty() method.

Code Block

bgColor	#FFcccc

class Vector {
  private int val = 1;

  public boolean isEmpty() {
    if (val == 1) {   // compares with 1 instead of 0
      return true;
    } else {
      return false;
    }
  }
  // other functionality is same as java.util.Vector
}

// import java.util.Vector; omitted

public class VectorUser {
  public static void main(String[] args) {
    Vector v = new Vector();
    if (v.isEmpty()) {
      System.out.println("Vector is empty");
    }
  }
}

Compliant Solution (Class Name)

This compliant solution uses a different name for the class, preventing any potential shadowing.

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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}}.

Risk Assessment

Name reuse decreases the readability and maintainability of code.

Recommendation	Severity	Likelihood	Remediation Cost	Priority	Level
DCL05-J	low	unlikely	medium	P2	L3

Automated Detection

An automated tool can easily detect reuse of the set of names representing public classes or interfaces from the Java Standard Library.

Related Guidelines

C Secure Coding Standard

"PRE04-C. Do not reuse a standard header file name"

C++ Secure Coding Standard

"PRE04-CPP. Do not reuse a standard header file name"

Bibliography

<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="21cb5a893a681e31-5e0d3563-400841e4-9d7ba6b8-f3bfe1ff03b7028cd4d92d82"><ac:plain-text-body><![CDATA[	[[JLS 2005	AA. Bibliography#JLS 05]]	[§6.3.2, "Obscured Declarations"	http://java.sun.com/docs/books/jls/third_edition/html/names.html#6.3.2]	]]></ac:plain-text-body></ac:structured-macro>
	§6.3.1, "Shadowing Declarations"
	§7.5.2, "Type-Import-On_Demand Declaration"
	§14.4.3, "Shadowing of Names by Local Variables"
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="4b5ae1a624d137e2-f5988dd6-4d5d4ff6-833ab64d-06c85285dfd43d5f5b6d7d9b"><ac:plain-text-body><![CDATA[	[[FindBugs 2008	AA. Bibliography#FindBugs 08]]	]]></ac:plain-text-body></ac:structured-macro>
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="b507f219df15664b-eb378a47-49f54e9a-bc24b353-d458ae3b40cbc8e99bbb1fa3"><ac:plain-text-body><![CDATA[	[[Bloch 2005	AA. Bibliography#Bloch 05]]	Puzzle 67: All Strung Out	]]></ac:plain-text-body></ac:structured-macro>
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="d1a940eda38d2563-27a167e3-41594c85-9cb29c79-0e6cc358de4736e1073c902c"><ac:plain-text-body><![CDATA[	[[Bloch 2008	AA. Bibliography#Bloch 08]]	Item 16: Prefer interfaces to abstract classes	]]></ac:plain-text-body></ac:structured-macro>

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