MethodLength

Since Checkstyle 3.0

Description

Checks for long methods and constructors.

Rationale: If a method becomes very long it is hard to understand. Therefore, long methods should usually be refactored into several individual methods that focus on a specific task.

Properties

name description type default value since
countEmpty Control whether to count empty lines and comments. boolean true 3.2
max Specify the maximum number of lines allowed. int 150 3.0
tokens tokens to check subset of tokens METHOD_DEF , CTOR_DEF , COMPACT_CTOR_DEF . METHOD_DEF , CTOR_DEF , COMPACT_CTOR_DEF . 3.0

Examples

To configure the check so that it accepts at most 4 lines: 

<module name="Checker">
  <module name="TreeWalker">
    <module name="MethodLength">
      <property name="max" value="4"/>
    </module>
  </module>
</module>

Example:

public class Example1 {

  // violation below, 'Method Example1 length is 5 lines (max allowed is 4)'
  public Example1() {
    int var1 = 2;
    int var2 = 4;
    int sum = var1 + var2;
  }

  // ok, as it is less than 4 lines
  public Example1(int a)  {
    int var1 = 2;
    int sum = var1 + a;
  }

  // violation below, 'Method firstMethod length is 6 lines (max allowed is 4)'
  public void firstMethod() {
    int index = 0;
    if (index < 5) {
      index++;
    }
  }

  public void secondMethod() {
    // comments are counted by default
    System.out.println("line 3");
  }

  // violation below, 'Method thirdMethod length is 5 lines (max allowed is 4)'
  public void thirdMethod() {

    // empty line above is counted by default,just like this comment
    System.out.println("line 4");
  }

  record MyBadRecord() {
    // violation below, 'Method MyBadRecord length is 5 lines (max allowed is 4)'
    public MyBadRecord {

      System.out.println("line3");
      System.out.println("line4");
    }
  }
}

To configure the check so that it accepts methods with at most 4 lines: 

<module name="Checker">
  <module name="TreeWalker">
    <module name="MethodLength">
      <property name="tokens" value="METHOD_DEF"/>
      <property name="max" value="4"/>
    </module>
  </module>
</module>

Example:

public class Example2 {

  // ok, CTOR_DEF is not in configured tokens
  public Example2()  {
    int var1 = 2;
    int var2 = 4;
    int sum = var1 + var2;
  }

  // ok, CTOR_DEF is not in configured tokens
  public Example2(int a)  {
    int var1 = 2;
    int sum = var1 + a;
  }

  // violation below, 'Method firstMethod length is 6 lines (max allowed is 4)'
  public void firstMethod() {
    int index = 0;
    if (index < 5) {
      index++;
    }
  }

  public void secondMethod() {
    // comments are counted by default
    System.out.println("line 3");
  }

  // violation below, 'Method thirdMethod length is 5 lines (max allowed is 4)'
  public void thirdMethod() {

    // empty line above is counted by default,just like this comment
    System.out.println("line 4");
  }

  record MyBadRecord() {
    // ok, COMPACT_CTOR_DEF is not in configured tokens
    public MyBadRecord {

      System.out.println("line3");
      System.out.println("line4");
    }
  }
}

To configure the check so that it accepts methods with at most 4 lines, not counting empty lines and comments: 

<module name="Checker">
  <module name="TreeWalker">
    <module name="MethodLength">
      <property name="tokens" value="METHOD_DEF"/>
      <property name="max" value="4"/>
      <property name="countEmpty" value="false"/>
    </module>
  </module>
</module>

Example:

public class Example3 {

  // ok, CTOR_DEF is not in configured tokens
  public Example3()  {
    int var1 = 2;
    int var2 = 4;
    int sum = var1 + var2;
  }

  // ok, CTOR_DEF is not in configured tokens
  public Example3(int a)  {
    int var1 = 2;
    int sum = var1 + a;
  }

  // violation below, 'Method firstMethod length is 6 lines (max allowed is 4)'
  public void firstMethod() {
    int index = 0;
    if (index < 5) {
      index++;
    }
  }

  public void secondMethod() {
    // countEmpty property is false,so this line doesn't count
    System.out.println("line 3");
  }

  public void thirdMethod() {

    // countEmpty property is false,so this line and the line above don't count
    System.out.println("line 4");
  }

  record MyBadRecord() {
    // ok, COMPACT_CTOR_DEF is not in configured tokens
    public MyBadRecord {

      System.out.println("line3");
      System.out.println("line4");
    }
  }
}

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.sizes

Parent Module

TreeWalker