Import Statements

These rules deal with different problems that can occur with import statements.

DuplicateImports

Since: PMD 0.5

Duplicate or overlapping import statements should be avoided.

This rule is defined by the following Java class:net.sourceforge.pmd.lang.java.rule.imports.DuplicateImportsRule

Example(s):

import java.lang.String;
import java.lang.*;
public class Foo {}

    

DontImportJavaLang

Since: PMD 0.5

Avoid importing anything from the package 'java.lang'. These classes are automatically imported (JLS 7.5.3).

This rule is defined by the following Java class:net.sourceforge.pmd.lang.java.rule.imports.DontImportJavaLangRule

Example(s):

import java.lang.String;	// this is unnecessary

public class Foo {}

// --- in another source code file...

import java.lang.*;	// this is bad

public class Foo {}

    

UnusedImports

Since: PMD 1.0

Avoid the use of unused import statements to prevent unwanted dependencies.

This rule is defined by the following Java class:net.sourceforge.pmd.lang.java.rule.imports.UnusedImportsRule

Example(s):

// this is bad
import java.io.File;
public class Foo {}

    

ImportFromSamePackage

Since: PMD 1.02

There is no need to import a type that lives in the same package.

This rule is defined by the following Java class:net.sourceforge.pmd.lang.java.rule.imports.ImportFromSamePackageRule

Example(s):
 
 package foo;
 
 import foo.Buz; // no need for this
 import foo.*; // or this
 
 public class Bar{}
 
     

TooManyStaticImports

Since: PMD 4.1

If you overuse the static import feature, it can make your program unreadable and unmaintainable, polluting its namespace with all the static members you import. Readers of your code (including you, a few months after you wrote it) will not know which class a static member comes from (Sun 1.5 Language Guide).

.[count(ImportDeclaration[@Static = 'true']) > $maximumStaticImports]
	             
Example(s):
import static Lennon;
import static Ringo;
import static George;
import static Paul;
import static Yoko; // Too much !
		  

This rule has the following properties:

Name Default Value Description
maximumStaticImports 4 All static imports can be disallowed by setting this to 0

UnnecessaryFullyQualifiedName

Since: PMD 5.0

Import statements allow the use of non-fully qualified names. The use of a fully qualified name which is covered by an import statement is redundant. Consider using the non-fully qualified name.

This rule is defined by the following Java class:net.sourceforge.pmd.lang.java.rule.imports.UnnecessaryFullyQualifiedNameRule

Example(s):
import java.util.List;

public class Foo {
   private java.util.List list1; // Unnecessary FQN
   private List list2; // More appropriate given import of 'java.util.List'
}