LambdaParameterName

Since Checkstyle 8.11

Description

Checks lambda parameter names.

Properties

name	description	type	default value	since
format	Sets the pattern to match valid identifiers.	Pattern	`"^([a-z][a-zA-Z0-9]*\|_)$"`	8.11

Examples

To configure the check:


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

Code Example:


class Example1 {
  Function<String, String> function1 = s -> s.toLowerCase();
  Function<String, String> function2 =
          S -> S.toLowerCase(); // violation 'Name 'S' must match pattern'
}

An example of how to configure the check for names that begin with a lower case letter, followed by letters is:


<module name="Checker">
  <module name="TreeWalker">
    <module name="LambdaParameterName">
      <property name="format" value="^[a-z]([a-zA-Z]+)*$"/>
    </module>
  </module>
</module>

Code Example:


class Example2 {
  Function<String, String> function1 = str -> str.toUpperCase().trim();
  Function<String, String> function2 = _s -> _s.trim();
  // violation above 'Name '_s' must match pattern'

  public boolean myMethod(String sentence) {
    return Stream.of(sentence.split(" "))
            .map(word -> word.trim())
            .anyMatch(Word -> "in".equals(Word));
    // violation above 'Name 'Word' must match pattern'
  }
}

Example of Usage

Violation Messages

name.invalidPattern

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.naming

Parent Module

TreeWalker