AvoidStarImport

Since Checkstyle 3.0

Description

Checks that there are no import statements that use the * notation.

Rationale: Importing all classes from a package or static members from a class leads to tight coupling between packages or classes and might lead to problems when a new version of a library introduces name clashes.

Notes

Note that property excludes is not recursive, subpackages of excluded packages are not automatically excluded.

Properties

name	description	type	default value	since
allowClassImports	Control whether to allow starred class imports like `import java.util.*;`.	boolean	`false`	5.3
allowStaticMemberImports	Control whether to allow starred static member imports like `import static org.junit.Assert.*;`.	boolean	`false`	5.3
excludes	Specify packages where starred class imports are allowed and classes where starred static member imports are allowed.	String[]	`{}`	3.2
maxAllowedStarImports	Control how many star imports are allowed.	int	`0`	13.5.0

Examples

To configure the check:


<module name="Checker">
  <module name="TreeWalker">
    <module name="AvoidStarImport"/>
  </module>
</module>

Example:


import java.util.Scanner;
import java.io.*; // violation, 'Using the '.*' form of import should be avoided.'
import static java.lang.Math.*; // violation, 'form of import should be avoided.'
import java.util.*; // violation, 'Using the '.*' form of import should be avoided.'
import java.net.*; // violation, 'Using the '.*' form of import should be avoided.'

To configure the check so that star imports from packages java.io and java.net as well as static members from class java.lang.Math are allowed:


<module name="Checker">
  <module name="TreeWalker">
    <module name="AvoidStarImport">
      <property name="excludes" value="java.io,java.net,java.lang.Math"/>
    </module>
  </module>
</module>

Example:


import java.util.Scanner;
import java.io.*;
import static java.lang.Math.*;
import java.util.*; // violation, 'Using the '.*' form of import should be avoided.'
import java.net.*;

To configure the check so that star imports from all packages are allowed:


<module name="Checker">
  <module name="TreeWalker">
    <module name="AvoidStarImport">
      <property name="allowClassImports" value="true"/>
    </module>
  </module>
</module>

Example:


import java.util.Scanner;
import java.io.*;
import static java.lang.Math.*; // violation, 'form of import should be avoided.'
import java.util.*;
import java.net.*;

To configure the check so that starred static member imports from all packages are allowed:


<module name="Checker">
  <module name="TreeWalker">
    <module name="AvoidStarImport">
      <property name="allowStaticMemberImports" value="true"/>
    </module>
  </module>
</module>

Example:


import java.util.Scanner;
import java.io.*; // violation, 'Using the '.*' form of import should be avoided.'
import static java.lang.Math.*;
import java.util.*; // violation, 'Using the '.*' form of import should be avoided.'
import java.net.*; // violation, 'Using the '.*' form of import should be avoided.'

To configure the check so that star imports from packages java.io and java.net are allowed:


<module name="Checker">
  <module name="TreeWalker">
    <module name="AvoidStarImport">
      <property name="allowClassImports" value="true"/>
      <property name="excludes" value="java.io,java.net"/>
    </module>
  </module>
</module>

Example:


import java.util.Scanner;
import java.io.*;
import static java.lang.Math.*; // violation, 'form of import should be avoided.'
import java.util.*;
import java.net.*;

To configure the check so that star imports from packages java.io and java.net as well as static members imports from all packages are allowed:


<module name="Checker">
  <module name="TreeWalker">
    <module name="AvoidStarImport">
      <property name="allowStaticMemberImports" value="true"/>
      <property name="excludes" value="java.io,java.net"/>
    </module>
  </module>
</module>

Example:


import java.util.Scanner;
import java.io.*;
import static java.lang.Math.*;
import java.util.*; // violation, 'Using the '.*' form of import should be avoided.'
import java.net.*;

To configure the check according to OpenJDK guidelines, where at most one star import is allowed per file:


<module name="Checker">
  <module name="TreeWalker">
    <module name="AvoidStarImport">
      <property name="maxAllowedStarImports" value="1"/>
    </module>
  </module>
</module>

Example:


import java.util.Scanner;
import java.io.*;
import static java.lang.Math.*; // violation, 'Only '1' star import is allowed per file.'
import java.util.*; // violation, 'Only '1' star import is allowed per file.'
import java.net.*; // violation, 'Only '1' star import is allowed per file.'

Example of Usage

Violation Messages

All messages can be customized if the default message doesn't suit you. Please see the documentation to learn how to.

Fully Qualified Name

com.puppycrawl.tools.checkstyle.checks.imports.AvoidStarImportCheck

Use this fully qualified class name in configuration when an exact class reference is required.

Parent Module

TreeWalker