Class MethodLengthCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable

    public class MethodLengthCheck
    extends AbstractCheck

    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.

    • Property max - Specify the maximum number of lines allowed. Type is int. Default value is 150.
    • Property countEmpty - Control whether to count empty lines and comments. Type is boolean. Default value is true.
    • Property tokens - tokens to check Type is java.lang.String[]. Validation type is tokenSet. Default value is: METHOD_DEF, CTOR_DEF, COMPACT_CTOR_DEF.

    To configure the check:

     <module name="MethodLength"/>
     

    Example:

     public class MyClass {
       public MyClass() {  // constructor (line 1)
            /* line 2
                ...
               line 150 */
       } // line 151, violation, as it is over 150
    
       public void firstExample() { // line 1
    
           // line 3
           System.out.println("line 4");
           /* line 5
              line 6 */
       } // line 7, OK, as it is less than 150
    
       public void secondExample() { // line 1
           // line 2
           System.out.println("line 3");
    
           /* line 5
               ...
              line 150 */
       } // line 151, violation, as it is over 150
     }
     

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

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

    Example:

     public class MyTest {
       public MyTest()  {            // constructor (line 1)
           int var1 = 2;             // line 2
           int var2 = 4;             // line 3
           int sum = var1 + var2;  // line 4
       } // line 5, OK, constructor is not mentioned in the tokens
    
       public void firstMethod() { // line 1
           // comment (line 2)
           System.out.println("line 3");
       } // line 4, OK, as it allows at most 4 lines
    
       public void secondMethod() { // line 1
           int index = 0;   // line 2
           if (index < 5) { // line 3
               index++;     // line 4
           }                // line 5
       } // line 6, violation, as it is over 4 lines
    
       public void thirdMethod() { // line 1
    
           // comment (line 3)
           System.out.println("line 4");
       } // line 5, violation, as it is over 4 lines
     }
     

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

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

    Example:

     public class MyTest {
       public MyTest()  {          // constructor (line 1)
           int var1 = 2;           // line 2
           int var2 = 4;           // line 3
           int sum = var1 + var2;  // line 4
       } // line 5, OK, constructor is not mentioned in the tokens
    
       public void firstMethod() { // line 1
           // comment - not counted as line
           System.out.println("line 2");
       } // line 3, OK, as it allows at most 4 lines
    
       public void secondMethod() { // line 1
           int index = 0;   // line 2
           if (index < 5) { // line 3
               index++;     // line 4
           }                // line 5
       } // line 6, violation, as it is over 4 lines
    
       public void thirdMethod() { // line 1
    
           // comment - not counted as line
           System.out.println("line 2");
       } // line 3, OK, as it allows at most 4 lines
     }
     

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • maxLen.method
    Since:
    3.0
    • Field Detail

      • countEmpty

        private boolean countEmpty
        Control whether to count empty lines and comments.
      • max

        private int max
        Specify the maximum number of lines allowed.
    • Method Detail

      • getAcceptableTokens

        public int[] getAcceptableTokens()
        Description copied from class: AbstractCheck
        The configurable token set. Used to protect Checks against malicious users who specify an unacceptable token set in the configuration file. The default implementation returns the check's default tokens.
        Specified by:
        getAcceptableTokens in class AbstractCheck
        Returns:
        the token set this check is designed for.
        See Also:
        TokenTypes
      • getLengthOfBlock

        private static int getLengthOfBlock​(DetailAST openingBrace,
                                            DetailAST closingBrace)
        Returns length of code.
        Parameters:
        openingBrace - block opening brace
        closingBrace - block closing brace
        Returns:
        number of lines with code for current block
      • countUsedLines

        private static int countUsedLines​(DetailAST ast)
        Count number of used code lines without comments.
        Parameters:
        ast - start ast
        Returns:
        number of used lines of code
      • setMax

        public void setMax​(int length)
        Setter to specify the maximum number of lines allowed.
        Parameters:
        length - the maximum length of a method.
      • setCountEmpty

        public void setCountEmpty​(boolean countEmpty)
        Setter to control whether to count empty lines and comments.
        Parameters:
        countEmpty - whether to count empty and comments.