freeacs/freeacs

Utility classes, which are collections of static members, are not meant to be instantiated. Even abstract utility classes, which can be extended, should not have public constructors.

Java adds an implicit public constructor to every class which does not define at least one explicitly. Hence, at least one non-public constructor should be defined.

Noncompliant Code Example

class StringUtils { // Noncompliant

  public static String concatenate(String s1, String s2) {
    return s1 + s2;
  }

}

Compliant Solution

class StringUtils { // Compliant

  private StringUtils() {
    throw new IllegalStateException("Utility class");
  }

  public static String concatenate(String s1, String s2) {
    return s1 + s2;
  }

}

Exceptions

When class contains public static void main(String[] args) method it is not considered as utility class and will be ignored by this rule.

Checks for empty line separators after header, package, all import declarations,fields, constructors, methods, nested classes,static initializers and instance initializers.

ATTENTION: empty line separator is required between token siblings,not after line where token is found.If token does not have same type sibling then empty lineis required at its end (for example for CLASS_DEF it is after '}').Also, trailing comments are skipped.

ATTENTION: violations from multiple empty lines cannot be suppressed via XPath:#8179.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.