checkstyle – CustomImportOrder

CustomImportOrder

Since Checkstyle 5.8

Description

Checks that the groups of import declarations appear in the order specified by the user. If there is an import but its group is not specified in the configuration such an import should be placed at the end of the import list.

Rule Description

The rule consists of:

STATIC group. This group sets the ordering of static imports.
SAME_PACKAGE(n) group. This group sets the ordering of the same package imports. Imports are considered on SAME_PACKAGE group if n first domains in package name and import name are identical:
```
package java.util.concurrent.locks;

import java.io.File;
import java.util.*; //#1
import java.util.List; //#2
import java.util.StringTokenizer; //#3
import java.util.concurrent.*; //#4
import java.util.concurrent.AbstractExecutorService; //#5
import java.util.concurrent.locks.LockSupport; //#6
import java.util.regex.Pattern; //#7
import java.util.regex.Matcher; //#8
            
```
If we have SAME_PACKAGE(3) on configuration file, imports #4-6 will be considered as a SAME_PACKAGE group (java.util.concurrent.*, java.util.concurrent.AbstractExecutorService, java.util.concurrent.locks.LockSupport). SAME_PACKAGE(2) will include #1-8. SAME_PACKAGE(4) will include only #6. SAME_PACKAGE(5) will result in no imports assigned to SAME_PACKAGE group because actual package java.util.concurrent.locks has only 4 domains.
THIRD_PARTY_PACKAGE group. This group sets ordering of third party imports. Third party imports are all imports except STATIC, SAME_PACKAGE(n), STANDARD_JAVA_PACKAGE and SPECIAL_IMPORTS.
STANDARD_JAVA_PACKAGE group. By default, this group sets ordering of standard java/javax imports.
SPECIAL_IMPORTS group. This group may contain some imports that have particular meaning for the user.

Notes

Rules are configured as a comma-separated ordered list.

Note: '###' group separator is deprecated (in favor of a comma-separated list), but is currently supported for backward compatibility.

To set RegExps for THIRD_PARTY_PACKAGE and STANDARD_JAVA_PACKAGE groups use thirdPartyPackageRegExp and standardPackageRegExp options.

Pretty often one import can match more than one group. For example, static import from standard package or regular expressions are configured to allow one import match multiple groups. In this case, group will be assigned according to priorities:

STATIC has top priority
SAME_PACKAGE has second priority
STANDARD_JAVA_PACKAGE and SPECIAL_IMPORTS will compete using "best match" rule: longer matching substring wins; in case of the same length, lower position of matching substring wins; if position is the same, order of rules in configuration solves the puzzle.
THIRD_PARTY has the least priority

Few examples to illustrate "best match":

1. patterns STANDARD_JAVA_PACKAGE = "Check", SPECIAL_IMPORTS="ImportOrderCheck" and input file:

import com.puppycrawl.tools.checkstyle.checks.imports.CustomImportOrderCheck;
import com.puppycrawl.tools.checkstyle.checks.imports.ImportOrderCheck;

Result: imports will be assigned to SPECIAL_IMPORTS, because matching substring length is 16. Matching substring for STANDARD_JAVA_PACKAGE is 5.

2. patterns STANDARD_JAVA_PACKAGE = "Check", SPECIAL_IMPORTS="Avoid" and file:

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

Result: import will be assigned to SPECIAL_IMPORTS. Matching substring length is 5 for both patterns. However, "Avoid" position is lower than "Check" position.

Properties

name	description	type	default value	since
customImportOrderRules	Specify ordered list of import groups.	String[]	`{}`	5.8
separateLineBetweenGroups	Force empty line separator between import groups.	boolean	`true`	5.8
sortImportsInGroupAlphabetically	Force grouping alphabetically, in ASCII sort order.	boolean	`false`	5.8
specialImportsRegExp	Specify RegExp for SPECIAL_IMPORTS group imports.	Pattern	`"^$"`	5.8
standardPackageRegExp	Specify RegExp for STANDARD_JAVA_PACKAGE group imports.	Pattern	`"^(java\|javax)\."`	5.8
thirdPartyPackageRegExp	Specify RegExp for THIRD_PARTY_PACKAGE group imports.	Pattern	`".*"`	5.8

Examples

To configure the check :

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

Example:

package com.company;
import org.apache.commons.io.FileUtils; // OK
import static java.util.*; // OK
import java.time.*; // OK
import static java.io.*; // OK
import com.puppycrawl.tools.checkstyle.checks.imports.CustomImportOrderCheck; // OK
import com.puppycrawl.tools.checkstyle.checks.imports.ImportOrderCheck; // OK

To configure the check so that it checks in the order (static imports,standard java packages,third party package):

<module name="Checker">
  <module name="TreeWalker">
    <module name="CustomImportOrder">
      <property name="customImportOrderRules"
        value="STATIC, STANDARD_JAVA_PACKAGE, THIRD_PARTY_PACKAGE"/>
    </module>
  </module>
</module>

Example:

package com.company;

import static java.util.*; // OK

import java.time.*; // OK
import javax.net.*; // OK
import static java.io.*; // violation as static imports should be in top

import org.apache.commons.io.FileUtils; // OK
import com.puppycrawl.tools.checkstyle.checks.imports.CustomImportOrderCheck; // OK
import com.puppycrawl.tools.checkstyle.checks.imports.ImportOrderCheck; // OK

To configure the check such that only java packages are included in standard java packages

<module name="Checker">
  <module name="TreeWalker">
    <module name="CustomImportOrder">
      <property name="customImportOrderRules"
        value="STATIC, STANDARD_JAVA_PACKAGE, THIRD_PARTY_PACKAGE"/>
      <property name="standardPackageRegExp" value="^java\."/>
    </module>
  </module>
</module>

Example:

package com.company;

import static java.util.*; // OK
import static java.io.*; // OK

import java.time.*; // OK
import javax.net.*; // violation as it is not included in standard java package group.

import org.apache.commons.io.FileUtils; // violation
import com.puppycrawl.tools.checkstyle.checks.imports.CustomImportOrderCheck; // OK
import com.puppycrawl.tools.checkstyle.checks.imports.ImportOrderCheck; // OK

To configure the check to include only "com" packages as third party group imports:

<module name="Checker">
  <module name="TreeWalker">
    <module name="CustomImportOrder">
      <property name="customImportOrderRules"
        value="STATIC, STANDARD_JAVA_PACKAGE, SPECIAL_IMPORTS, THIRD_PARTY_PACKAGE"/>
      <property name="thirdPartyPackageRegExp" value="^com\."/>
    </module>
  </module>
</module>

Example:

package com.company;

import static java.util.*; // OK
import static java.io.*; // OK

import java.time.*; // OK
import javax.net.*; // OK

import org.apache.commons.io.FileUtils; // violation(should be in end)
import com.puppycrawl.tools.checkstyle.checks.imports.CustomImportOrderCheck; // violation
import com.puppycrawl.tools.checkstyle.checks.imports.ImportOrderCheck; // OK

To configure the check to force some packages in special import group:

<module name="Checker">
  <module name="TreeWalker">
    <module name="CustomImportOrder">
      <property name="customImportOrderRules"
        value="STATIC, SPECIAL_IMPORTS, STANDARD_JAVA_PACKAGE"/>
      <property name="specialImportsRegExp" value="^org\."/>
    </module>
  </module>
</module>

Example:

package com.company;

import static java.util.*; // OK
import static java.io.*; // OK

import org.json.JSONObject; // OK

import java.time.*; // OK
import javax.net.*; // OK

import org.apache.commons.io.FileUtils; // violation

To configure the check such that empty line separator between two groups is enabled:

<module name="Checker">
  <module name="TreeWalker">
    <module name="CustomImportOrder">
      <property name="customImportOrderRules"
        value="STATIC, STANDARD_JAVA_PACKAGE, SPECIAL_IMPORTS, THIRD_PARTY_PACKAGE"/>
      <property name="specialImportsRegExp" value="^org\."/>
      <property name="thirdPartyPackageRegExp" value="^com\."/>
      <property name="separateLineBetweenGroups" value="true"/>
    </module>
  </module>
</module>

Example:

package com.company;

import static java.util.*; // OK
import static java.io.*; // OK

import java.time.*; // OK
import javax.net.*; // OK
import org.apache.commons.io.FileUtils; // violation
import com.puppycrawl.tools.checkstyle.checks.imports.CustomImportOrderCheck; // violation
import com.puppycrawl.tools.checkstyle.checks.imports.ImportOrderCheck; // OK

To configure the check such that import groups are forced to be sorted alphabetically:

<module name="Checker">
  <module name="TreeWalker">
    <module name="CustomImportOrder">
      <property name="customImportOrderRules"
        value="STATIC, STANDARD_JAVA_PACKAGE, SPECIAL_IMPORTS, THIRD_PARTY_PACKAGE"/>
      <property name="specialImportsRegExp" value="^org\."/>
      <property name="thirdPartyPackageRegExp" value="^com\."/>
      <property name="separateLineBetweenGroups" value="false"/>
      <property name="sortImportsInGroupAlphabetically" value="true"/>
    </module>
  </module>
</module>

Example:

package com.company;

import static java.util.*; // OK
import static java.io.*; // Violation since it should come before"java.util"

import java.time.*; // OK
import javax.net.*; // OK
import org.apache.commons.io.FileUtils; // OK
import com.puppycrawl.tools.checkstyle.checks.imports.CustomImportOrderCheck; // OK
import com.puppycrawl.tools.checkstyle.checks.imports.ImportOrderCheck; // OK

To configure the check so that it matches default Eclipse formatter configuration (tested on Kepler and Luna releases):

group of static imports is on the top
groups of non-static imports: "java" and "javax" packages first, then "org" and then all other imports
imports will be sorted in the groups
groups are separated by single blank line

Notes:

"com" package is not mentioned on configuration, because it is ignored by Eclipse Kepler and Luna (looks like Eclipse defect)
configuration below doesn't work in all 100% cases due to inconsistent behavior prior to Mars release, but covers most scenarios

<module name="Checker">
  <module name="TreeWalker">
    <module name="CustomImportOrder">
      <property name="customImportOrderRules"
        value="STATIC, STANDARD_JAVA_PACKAGE, SPECIAL_IMPORTS"/>
      <property name="specialImportsRegExp" value="^org\."/>
      <property name="sortImportsInGroupAlphabetically" value="true"/>
      <property name="separateLineBetweenGroups" value="true"/>
    </module>
  </module>
</module>

Example:

package com.company;

import static java.util.*; // OK
import static java.io.*; // Violation since it should come before"java.util"

import java.time.*; // OK
import javax.net.*; // OK
import org.apache.commons.io.FileUtils; // Violation should be separated by space

import com.puppycrawl.tools.checkstyle.checks.imports.CustomImportOrderCheck; // OK
import com.puppycrawl.tools.checkstyle.checks.imports.ImportOrderCheck; // OK

To configure the check so that it matches default Eclipse formatter configuration (tested on Mars release):

group of static imports is on the top
groups of non-static imports: "java" and "javax" packages first, then "org" and "com", then all other imports as one group
imports will be sorted in the groups
groups are separated by one blank line

<module name="Checker">
  <module name="TreeWalker">
    <module name="CustomImportOrder">
      <property name="customImportOrderRules"
        value="STATIC, STANDARD_JAVA_PACKAGE, SPECIAL_IMPORTS, THIRD_PARTY_PACKAGE"/>
      <property name="specialImportsRegExp" value="^org\."/>
      <property name="thirdPartyPackageRegExp" value="^com\."/>
      <property name="sortImportsInGroupAlphabetically" value="true"/>
      <property name="separateLineBetweenGroups" value="true"/>
    </module>
  </module>
</module>

Example:

package com.company;

import static java.io.*; // OK
import static java.util.*; // OK

import java.time.*; // OK
import javax.net.*; // OK

import com.puppycrawl.tools.checkstyle.checks.imports.CustomImportOrderCheck; // Violation
import com.puppycrawl.tools.checkstyle.checks.imports.ImportOrderCheck; // Violation

import org.apache.commons.io.FileUtils;

To configure the check so that it matches default IntelliJ IDEA formatter configuration (tested on v14):

group of static imports is on the bottom
groups of non-static imports: all imports except of "javax" and "java", then "javax" and "java"
imports will be sorted in the groups
groups are separated by one blank line

Note: "separated" option is disabled because IDEA default has blank line between "java" and static imports, and no blank line between "javax" and "java"

<module name="Checker">
  <module name="TreeWalker">
    <module name="CustomImportOrder">
      <property name="customImportOrderRules"
        value="THIRD_PARTY_PACKAGE, SPECIAL_IMPORTS, STANDARD_JAVA_PACKAGE, STATIC"/>
      <property name="specialImportsRegExp" value="^javax\."/>
      <property name="standardPackageRegExp" value="^java\."/>
      <property name="sortImportsInGroupAlphabetically" value="true"/>
      <property name="separateLineBetweenGroups" value="false"/>
    </module>
  </module>
</module>

Example:

package com.company;

import static java.io.*; // OK
import static java.util.*; // OK

import java.time.*; // violation should be in standard package group
                   // below special import

import javax.net.*; // Violation should be in special import group

import org.apache.commons.io.FileUtils; // Violation should be in
                                       // THIRD PARTY PACKAGE GROUP
import com.puppycrawl.tools.checkstyle.checks.imports.CustomImportOrderCheck; // Violation
import com.puppycrawl.tools.checkstyle.checks.imports.ImportOrderCheck; // Violation

To configure the check so that it matches default NetBeans formatter configuration (tested on v8):

groups of non-static imports are not defined, all imports will be sorted as a one group
static imports are not separated, they will be sorted along with other imports

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

Example:

package com.company;

import static java.io.*; // OK
import static java.util.*; // OK
import java.time.*; // OK
import javax.net.*; // OK
import com.puppycrawl.tools.checkstyle.checks.imports.CustomImportOrderCheck; // OK
import com.puppycrawl.tools.checkstyle.checks.imports.ImportOrderCheck; // OK

import org.apache.commons.io.FileUtils; // should not be separated by line

To set RegExps for THIRD_PARTY_PACKAGE and STANDARD_JAVA_PACKAGE groups use thirdPartyPackageRegExp and standardPackageRegExp options.

<module name="Checker">
  <module name="TreeWalker">
    <module name="CustomImportOrder">
      <property name="customImportOrderRules"
        value="STATIC, SAME_PACKAGE(3), THIRD_PARTY_PACKAGE, STANDARD_JAVA_PACKAGE"/>
      <property name="thirdPartyPackageRegExp" value="^(com|org)\."/>
      <property name="standardPackageRegExp" value="^(java|javax)\."/>
    </module>
  </module>
</module>

Example:

package com.company;

import static java.io.*; // OK
import static java.util.*; // OK
import java.time.*; // violation
import javax.net.*; // violation

import com.puppycrawl.tools.checkstyle.checks.imports.CustomImportOrderCheck; // OK
import com.puppycrawl.tools.checkstyle.checks.imports.ImportOrderCheck; // OK
import org.apache.commons.io.FileUtils; // OK

Also, this check can be configured to force empty line separator between import groups. For example.

<module name="Checker">
  <module name="TreeWalker">
    <module name="CustomImportOrder">
      <property name="separateLineBetweenGroups" value="true"/>
    </module>
  </module>
</module>

Example:

package com.company;

import static java.io.*; // OK
import static java.util.*; // OK
import java.time.*; // OK
import javax.net.*; // OK
import com.puppycrawl.tools.checkstyle.checks.imports.CustomImportOrderCheck; // OK
import com.puppycrawl.tools.checkstyle.checks.imports.ImportOrderCheck; // OK
import org.apache.commons.io.FileUtils; // OK

It is possible to enforce ASCII sort order of imports in groups using the following configuration:

<module name="Checker">
  <module name="TreeWalker">
    <module name="CustomImportOrder">
      <property name="sortImportsInGroupAlphabetically" value="true"/>
    </module>
  </module>
</module>

Example of ASCII order:

import java.awt.Dialog;
import java.awt.Window;
import java.awt.color.ColorSpace;
import java.awt.Frame; // violation here - in ASCII order 'F' should go before 'c',
                       // as all uppercase come before lowercase letters

To force checking imports sequence such as:

package com.puppycrawl.tools.checkstyle.imports;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.Beta;
import com.google.common.annotations.VisibleForTesting;

import org.abego.treelayout.Configuration;

import static sun.tools.util.ModifierFilter.ALL_ACCESS;

import com.google.common.annotations.GwtCompatible; // violation here - should be in the
                                                    // THIRD_PARTY_PACKAGE group
import android.*;

configure as follows:

<module name="Checker">
  <module name="TreeWalker">
    <module name="CustomImportOrder">
      <property name="customImportOrderRules"
        value="SAME_PACKAGE(3), THIRD_PARTY_PACKAGE, STATIC, SPECIAL_IMPORTS"/>
      <property name="specialImportsRegExp" value="^android\."/>
    </module>
  </module>
</module>

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.

Package

com.puppycrawl.tools.checkstyle.checks.imports

Parent Module

TreeWalker

About

Documentation

Developers

Project Documentation

CustomImportOrder

Description

Rule Description

Notes

Properties

Examples

Example of Usage

Violation Messages

Package

Parent Module