LambdaBodyLength

Since Checkstyle 8.37

Description

Checks lambda body length.

Rationale: Similar to anonymous inner classes, if lambda body becomes very long it is hard to understand and to see the flow of the method where the lambda is defined. Therefore, long lambda body should usually be extracted to method.

Properties

name description type default value since
max Specify the maximum number of lines allowed. int 10 8.37

Examples

To configure the check to accept lambda bodies with up to 10 lines: 

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

Example: 

class Example1 {
  Runnable r = () -> { // OK, length is 10
    System.out.println(2); // line 2 of lambda
    System.out.println(3);
    System.out.println(4);
    System.out.println(5);
    System.out.println(6);
    System.out.println(7);
    System.out.println(8);
    System.out.println(9);
  }; // line 10
  Runnable r2 = () -> { // violation 'length is 11'
    System.out.println(2); // line 2 of lambda
    System.out.println(3);
    System.out.println(4);
    System.out.println(5);
    System.out.println(6);
    System.out.println(7);
    System.out.println(8);
    System.out.println(9);
    System.out.println(10);
  }; // line 11
  Runnable r3 = () -> // violation 'length is 11'
    "someString".concat("1") // line 1 of lambda
                .concat("2")
                .concat("3")
                .concat("4")
                .concat("5")
                .concat("6")
                .concat("7")
                .concat("8")
                .concat("9")
                .concat("10")
                .concat("11"); // line 11
}

To configure the check to accept lambda bodies with max 5 lines: 

<module name="Checker">
  <module name="TreeWalker">
    <module name="LambdaBodyLength">
      <property name="max" value="5"/>
    </module>
  </module>
</module>

Example: 

class Example2 {
  Runnable r = () -> { // OK, length is 5
    System.out.println(2);
    System.out.println(3);
    System.out.println(4);
  };
  Runnable r2 = () -> { // violation 'length is 6'
    System.out.println(2); // line 2 of lambda
    System.out.println(3);
    System.out.println(4);
    System.out.println(5);
  };

  Runnable r3 = () -> // violation 'length is 6'
    "someString".concat("1")
                .concat("2")
                .concat("3")
                .concat("4")
                .concat("5")
                .concat("6");
}

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