Standard Checks

The Standard Checkstyle Checks are applicable to general Java coding style and require no external libraries. The standard checks are included in the base distribution.

The site navigation menu lets you browse the individual checks by functionality.

Checkstyle provides many checks that you can apply to your source code. Below is an alphabetical reference, the site navigation menu provides a reference organized by functionality.

AbbreviationAsWordInName The Check validate abbreviations(consecutive capital letters) length in identifier name, it also allow in enforce camel case naming.
AbstractClassName Ensures that the names of abstract classes conforming to some regular expression.
AnnotationLocation Check location of annotation on language elements.
AnnotationUseStyle This check controls the style with the usage of annotations.
AnonInnerLength Checks for long anonymous inner classes.
ArrayTrailingComma Checks if array initialization contains optional trailing comma.
ArrayTypeStyle Checks the style of array type definitions.
AtclauseOrder Checks the order of at-clauses.
AvoidEscapedUnicodeCharacters Restrict using Unicode escapes.
AvoidInlineConditionals Detects inline conditionals.
AvoidNestedBlocks Finds nested blocks.
AvoidStarImport Check that finds import statements that use the * notation.
AvoidStaticImport Check that finds static imports.
BooleanExpressionComplexity Restricts nested boolean operators (&&, ||, &, | and ^) to a specified depth (default = 3).
CatchParameterName Checks that catch parameter names conform to a format specified by the format property.
ClassDataAbstractionCoupling This metric measures the number of instantiations of other classes within the given class.
ClassFanOutComplexity The number of other classes a given class relies on.
ClassTypeParameterName Checks that class type parameter names conform to a format specified by the format property.
CommentsIndentation Controls the indentation between comments and surrounding code.
ConstantName Checks that constant names conform to a format specified by the format property.
CovariantEquals Checks that if a class defines a covariant method equals, then it defines method equals(java.lang.Object).
CustomImportOrder Checks that the groups of import declarations appear in the order specified by the user.
CyclomaticComplexity Checks cyclomatic complexity against a specified limit.
DeclarationOrder Checks that the parts of a class or interface declaration appear in the order suggested by the Code Conventions for the Java Programming Language.
DefaultComesLast Check that the default is after all the cases in a switch statement.
DescendantToken Checks for restricted tokens beneath other tokens.
DesignForExtension Checks that classes are designed for inheritance.
EmptyBlock Checks for empty blocks.
EmptyCatchBlock Checks for empty catch blocks with few options to skip violation.
EmptyForInitializerPad Checks the padding of an empty for initializer; that is whether a space is required at an empty for initializer, or such spaces are forbidden.
EmptyForIteratorPad Checks the padding of an empty for iterator; that is whether a space is required at an empty for iterator, or such spaces are forbidden.
EmptyLineSeparator Checks for blank line separators.
EmptyStatement Detects empty statements (standalone ';').
EqualsAvoidNull Checks that any combination of String literals is on the left side of an equals() comparison.
EqualsHashCode Checks that classes that override equals() also override hashCode().
ExecutableStatementCount Restricts the number of executable statements to a specified limit (default = 30).
ExplicitInitialization Checks if any class or object member explicitly initialized to default for its type value (null for object references, zero for numeric types and char and false for boolean.
FallThrough Checks for fall through in switch statements Finds locations where a case contains Java code - but lacks a break, return, throw or continue statement.
FileLength Checks for long source files.
FileTabCharacter Checks to see if a file contains a tab character.
FinalClass Checks that class which has only private constructors is declared as final.
FinalLocalVariable Ensures that local variables that never get their values changed, must be declared final.
FinalParameters Check that method/constructor/catch/foreach parameters are final.
GenericWhitespace Checks that the whitespace around the Generic tokens < and > are correct to the typical convention.
Header Checks the header of the source against a fixed header file.
HiddenField Checks that a local variable or a parameter does not shadow a field that is defined in the same class.
HideUtilityClassConstructor Make sure that utility classes (classes that contain only static methods) do not have a public constructor.
IllegalCatch Catching java.lang.Exception, java.lang.Error or java.lang.RuntimeException is almost never acceptable.
IllegalImport Checks for imports from a set of illegal packages.
IllegalInstantiation Checks for illegal instantiations where a factory method is preferred.
IllegalThrows Throwing java.lang.Error or java.lang.RuntimeException is almost never acceptable.
IllegalToken Checks for illegal tokens.
IllegalTokenText Checks for illegal token text.
IllegalType Checks that particular class are never used as types in variable declarations, return values or parameters.
ImportControl Check that controls what packages can be imported in each package.
ImportOrder Ensures that groups of imports come in a specific order.
Indentation Checks correct indentation of Java Code.
InnerAssignment Checks for assignments in subexpressions, such as in String s = Integer.toString(i = 2);.
InnerTypeLast Check nested (internal) classes/interfaces are declared at the bottom of the class after all method and field declarations.
InterfaceIsType Implements Bloch, Effective Java, Item 17 - Use Interfaces only to define types.
InterfaceTypeParameterName Checks that interface type parameter names conform to a format specified by the format property.
JavadocMethod Checks the Javadoc of a method or constructor.
JavadocPackage Checks that all packages have a package documentation.
JavadocParagraph Checks Javadoc paragraphs.
JavadocStyle Custom Checkstyle Check to validate Javadoc.
JavadocTagContinuationIndentation Checks the indentation of the continuation lines in at-clauses.
JavadocType Checks the Javadoc of a type.
JavadocVariable Checks that a variable has Javadoc comment.
JavaNCSS This check calculates the Non Commenting Source Statements (NCSS) metric for Java source files and methods.
LeftCurly Checks the placement of left curly braces on types, methods and other blocks:
LineLength Checks for long lines.
LocalFinalVariableName Checks that local final variable names conform to a format specified by the format property.
LocalVariableName Checks that local, non-final variable names conform to a format specified by the format property.
MagicNumber Checks for magic numbers.
MemberName Checks that instance variable names conform to a format specified by the format property.
MethodCount Checks the number of methods declared in each type.
MethodLength Checks for long methods.
MethodName Checks that method names conform to a format specified by the format property.
MethodParamPad Checks the padding between the identifier of a method definition, constructor definition, method call, or constructor invocation; and the left parenthesis of the parameter list.
MethodTypeParameterName Checks that class type parameter names conform to a format specified by the format property.
MissingCtor Checks that classes (except abstract one) define a ctor and don't rely on the default one.
MissingDeprecated This class is used to verify that both the java.lang.Deprecated annotation is present and the @deprecated Javadoc tag is present when either is present.
MissingOverride This class is used to verify that the java.lang.Override annotation is present when the {@inheritDoc} javadoc tag is present.
MissingSwitchDefault Checks that switch statement has "default" clause.
ModifiedControlVariable Check for ensuring that for loop control variables are not modified inside the for block.
ModifierOrder Checks that the order of modifiers conforms to the suggestions in the Java Language specification, sections 8.1.1, 8.3.1 and 8.4.3.
MultipleStringLiterals Checks for multiple occurrences of the same string literal within a single file.
MultipleVariableDeclarations Checks that each variable declaration is in its own statement and on its own line.
MutableException Ensures that exceptions (defined as any class name conforming to some regular expression) are immutable.
NeedBraces Checks for braces around code blocks.
NestedForDepth Restricts nested for blocks to a specified depth (default = 1).
NestedIfDepth Restricts nested if-else blocks to a specified depth (default = 1).
NestedTryDepth Restricts nested try-catch-finally blocks to a specified depth (default = 1).
NewlineAtEndOfFile Checks that there is a newline at the end of each file.
NoClone Checks that the clone method is not overridden from the Object class.
NoFinalizer Checks that no method having zero parameters is defined using the name finalize.
NoLineWrap Checks that chosen statements are not line-wrapped.
NonEmptyAtclauseDescription Checks that the at-clause tag is followed by description .
NoWhitespaceAfter Checks that there is no whitespace after a token.
NoWhitespaceBefore Checks that there is no whitespace before a token.
NPathComplexity Checks the npath complexity against a specified limit (default = 200).
OneStatementPerLine Checks that there is only one statement per line.
OneTopLevelClass Checks that each top-level class, interfaces or enum resides in a source file of its own.
OperatorWrap Checks line wrapping for operators.
OuterTypeFilename Checks that the outer type name and the file name match.
OuterTypeNumber Checks for the number of defined types at the "outer" level.
OverloadMethodsDeclarationOrder Checks that overload methods are grouped together.
PackageAnnotation This check makes sure that all package annotations are in the file.
PackageDeclaration Ensures there is a package declaration and (optionally) in the correct directory.
PackageName Checks that package names conform to a format specified by the format property.
ParameterAssignment Disallow assignment of parameters.
ParameterName Checks that parameter names conform to a format specified by the format property.
ParameterNumber Checks the number of parameters that a method or constructor has.
ParenPad Checks the padding of parentheses; that is whether a space is required after a left parenthesis and before a right parenthesis, or such spaces are forbidden, with the exception that it does not check for padding of the right parenthesis at an empty for iterator.
RedundantImport Checks for imports that are redundant.
RedundantModifier Checks for redundant modifiers in interface and annotation definitions, final modifier on methods of final classes, inner interface declarations that are declared as static, non public class constructors and enum constructors, nested enum definitions that are declared as static.
Regexp A check that makes sure that a specified pattern exists (or not) in the file.
RegexpHeader Checks the header of the source against a header file that contains a
RegexpMultiline Implementation of a check that looks that matches across multiple lines in any file type.
RegexpOnFilename Implementation of a check that matches based on file and/or folder path.
RegexpSingleline Implementation of a check that looks for a single line in any file type.
RegexpSinglelineJava Implementation of a check that looks for a single line in Java files.
RequireThis Checks that code doesn't rely on the "this" default.
ReturnCount Restricts return statements to a specified count (default = 2).
RightCurly Checks the placement of right curly braces.
SeparatorWrap Checks line wrapping with separators.
SimplifyBooleanExpression Checks for overly complicated boolean expressions.
SimplifyBooleanReturn Checks for overly complicated boolean return statements.
SingleLineJavadoc Checks that a JavaDoc block which can fit on a single line and doesn't contain at-clauses
SingleSpaceSeparator Checks that non-whitespace characters are separated by no more than one whitespace.
StaticVariableName Checks that static, non-final variable names conform to a format specified by the format property.
StringLiteralEquality Checks that string literals are not used with == or !=.
SummaryJavadoc Checks that Javadoc summary sentence does not contain phrases that are not recommended to use.
SuperClone Checks that an overriding clone() method invokes super.clone().
SuperFinalize Checks that an overriding finalize() method invokes super.finalize().
SuppressWarnings This check allows you to specify what warnings that
ThrowsCount Restricts throws statements to a specified count (default = 4).
TodoComment A check for TODO comments.
TrailingComment The check to ensure that requires that comments be the only thing on a line.
Translation The TranslationCheck class helps to ensure the correct translation of code by checking property files for consistency regarding their keys.
TypecastParenPad Checks the padding of parentheses for typecasts.
TypeName Checks that type names conform to a format specified by the format property.
UncommentedMain Detects uncommented main methods.
UniqueProperties Detects duplicated keys in properties files.
UnnecessaryParentheses Checks if unnecessary parentheses are used in a statement or expression.
UnusedImports Checks for unused import statements.
UpperEll Checks that long constants are defined with an upper ell.
VariableDeclarationUsageDistance Checks the distance between declaration of variable and its first usage.
VisibilityModifier Checks visibility of class members.
WhitespaceAfter Checks that a token is followed by whitespace, with the exception that it does not check for whitespace after the semicolon of an empty for iterator.
WhitespaceAround Checks that a token is surrounded by whitespace.
WriteTag Outputs a JavaDoc tag as information.

Holder Checks

These checks aren't normal checks and are usually associated with a specialized filter to gather information the filter can't get on it's own.

FileContentsHolder Holds the current file contents for global access when configured as a TreeWalker sub-module.
SuppressWarningsHolder Maintains a set of check suppressions from SuppressWarnings annotations.