Description

Rationale: This check can be used to prototype checks and to find common bad practice such as calling ex.printStacktrace(), System.out.println(), System.exit(), etc.

Properties

Examples

To configure the default check:

<module name="Checker">
  <module name="RegexpSingleline" />
</module>
        

This configuration does not match to anything, so we do not provide any code example for it as no violation will ever be reported.

To configure the check to find occurrences of 'System.exit(' with some slack of allowing only one occurrence per file:

<module name="Checker">
  <module name="RegexpSingleline">
    <property name="format" value="System.exit\("/>
    <!-- next line not required as 0 is the default -->
    <property name="minimum" value="0"/>
    <property name="maximum" value="1"/>
  </module>
</module>
        

Example:

public class Example2 {
  void myFunction() {
    try {
      doSomething();
    } catch (Exception e) {
      System.exit(1); // OK, as only there is only one occurrence.
    }
  }

  void doSomething(){}
}
        

Example with violation:

public class Example3 {
  void myFunction() {
    try {
      doSomething();
      System.exit(0);
    } catch (Exception e) {
      System.exit(1); // violation, as there are more than one occurrence.
    }
  }

  void doSomething(){}
}
        

An example of how to configure the check to make sure a copyright statement is included in the file:

<module name="Checker">
  <module name="RegexpSingleline">
    <property name="format" value="^[ ]*\* This file is copyrighted"/>
    <property name="minimum" value="1"/>
    <!--  Need to specify a maximum, so 10 times is more than enough. -->
    <property name="maximum" value="10"/>
  </module>
</module>
        

Example:

/**
* This file is copyrighted under CC.
*/
public class Example4 {}
        

An example of how to configure the check to make sure a copyright statement is included in the file:

<module name="Checker">
  <module name="RegexpSingleline">
    <property name="format" value="^[ ]*\* This file is copyrighted"/>
    <property name="minimum" value="1"/>
    <!--  Need to specify a maximum, so 10 times is more than enough. -->
    <property name="maximum" value="10"/>
    <property name="message"
              value="File must contain copyright statement"/>
  </module>
</module>
        

Example with violation:

package com.puppycrawl.tools.checkstyle.checks.regexp.regexpsingleline;
/* violation on first line 'File must contain copyright statement' */
/**
 * MyClass as a configuration example.
 */
public class Example5 {}
        

An example of how to configure the check to make sure sql files contains the term 'license'.

<module name="Checker">
  <module name="RegexpSingleline">
      <property name="format" value="license"/>
      <property name="minimum" value="1"/>
      <property name="maximum" value="9999"/>
      <property name="ignoreCase" value="true"/>
      <!--  Configure a message to be shown on violation of the Check. -->
      <property name="message"
                value="File must contain at least one occurrence of 'license' term"/>
      <!--  Perform the Check only on files with SQL extension. -->
      <property name="fileExtensions" value="sql"/>
  </module>
</module>
        

Example:

/*
 AP 2.0 License. // Ok, Check ignores the case of the term.
*/
CREATE DATABASE MyDB;
        

Example with violation:

/* // violation, file doesn't contain the term.
 Example sql file.
*/
CREATE DATABASE MyDB;
        

Example of Usage

• Checkstyle Style
• Sun Style

Violation Messages

• regexp.exceeded
• regexp.minimum

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.regexp

Parent Module

Checker