Package com.puppycrawl.tools.checkstyle.checks.whitespace

Class GenericWhitespaceCheck

java.lang.Object
com.puppycrawl.tools.checkstyle.api.AutomaticBean
com.puppycrawl.tools.checkstyle.api.AbstractViolationReporter
com.puppycrawl.tools.checkstyle.api.AbstractCheck
com.puppycrawl.tools.checkstyle.checks.whitespace.GenericWhitespaceCheck
All Implemented Interfaces:
Configurable, Contextualizable
public class GenericWhitespaceCheck extends AbstractCheck

Checks that the whitespace around the Generic tokens (angle brackets) "<" and ">" are correct to the typical convention. The convention is not configurable.

Left angle bracket ("<"):

  • should be preceded with whitespace only in generic methods definitions.
  • should not be preceded with whitespace when it is precede method name or constructor.
  • should not be preceded with whitespace when following type name.
  • should not be followed with whitespace in all cases.

Right angle bracket (">"):

  • should not be preceded with whitespace in all cases.
  • should be followed with whitespace in almost all cases, except diamond operators and when preceding method name or constructor.

To configure the check: 

 <module name="GenericWhitespace"/>

Examples with correct spacing: 

 // Generic methods definitions
 public void <K, V extends Number> boolean foo(K, V) {}
 // Generic type definition
 class name<T1, T2, ..., Tn> {}
 // Generic type reference
 OrderedPair<String, Box<Integer>> p;
 // Generic preceded method name
 boolean same = Util.<Integer, String>compare(p1, p2);
 // Diamond operator
 Pair<Integer, String> p1 = new Pair<>(1, "apple");
 // Method reference
 List<T> list = ImmutableList.Builder<T>::new;
 // Method reference
 sort(list, Comparable::<String>compareTo);
 // Constructor call
 MyClass obj = new <String>MyClass();

Examples with incorrect spacing: 

 List< String> l; // violation, "<" followed by whitespace
 Box b = Box. <String>of("foo"); // violation, "<" preceded with whitespace
 public<T> void foo() {} // violation, "<" not preceded with whitespace

 List a = new ArrayList<> (); // violation, ">" followed by whitespace
 Map<Integer, String>m; // violation, ">" not followed by whitespace
 Pair<Integer, Integer > p; // violation, ">" preceded with whitespace

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

  • ws.followed
  • ws.illegalFollow
  • ws.notPreceded
  • ws.preceded
Since:
5.0

  • Field Details

    • MSG_WS_PRECEDED

      public static final String MSG_WS_PRECEDED
      A key is pointing to the warning message text in "messages.properties" file.
      See Also:

    • MSG_WS_FOLLOWED

      public static final String MSG_WS_FOLLOWED
      A key is pointing to the warning message text in "messages.properties" file.
      See Also:

    • MSG_WS_NOT_PRECEDED

      public static final String MSG_WS_NOT_PRECEDED
      A key is pointing to the warning message text in "messages.properties" file.
      See Also:

    • MSG_WS_ILLEGAL_FOLLOW

      public static final String MSG_WS_ILLEGAL_FOLLOW
      A key is pointing to the warning message text in "messages.properties" file.
      See Also:

    • OPEN_ANGLE_BRACKET

      private static final String OPEN_ANGLE_BRACKET
      Open angle bracket literal.
      See Also:

    • CLOSE_ANGLE_BRACKET

      private static final String CLOSE_ANGLE_BRACKET
      Close angle bracket literal.
      See Also:

    • depth

      private int depth
      Used to count the depth of a Generic expression.

  • Constructor Details

    • GenericWhitespaceCheck

      public GenericWhitespaceCheck()

  • Method Details

    • getDefaultTokens

      public int[] getDefaultTokens()
      Description copied from class: AbstractCheck
      Returns the default token a check is interested in. Only used if the configuration for a check does not define the tokens.
      Specified by:
      getDefaultTokens in class AbstractCheck
      Returns:
      the default tokens
      See Also:

    • 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:

    • getRequiredTokens

      public int[] getRequiredTokens()
      Description copied from class: AbstractCheck
      The tokens that this check must be registered for.
      Specified by:
      getRequiredTokens in class AbstractCheck
      Returns:
      the token set this must be registered for.
      See Also:

    • beginTree

      public void beginTree(DetailAST rootAST)
      Description copied from class: AbstractCheck
      Called before the starting to process a tree. Ideal place to initialize information that is to be collected whilst processing a tree.
      Overrides:
      beginTree in class AbstractCheck
      Parameters:
      rootAST - the root of the tree

    • visitToken

      public void visitToken(DetailAST ast)
      Description copied from class: AbstractCheck
      Called to process a token.
      Overrides:
      visitToken in class AbstractCheck
      Parameters:
      ast - the token to process

    • processEnd

      private void processEnd(DetailAST ast)
      Checks the token for the end of Generics.
      Parameters:
      ast - the token to check

    • processNestedGenerics

      private void processNestedGenerics(DetailAST ast, String line, int after)
      Process Nested generics.
      Parameters:
      ast - token
      line - line content
      after - position after

    • processSingleGeneric

      private void processSingleGeneric(DetailAST ast, String line, int after)
      Process Single-generic.
      Parameters:
      ast - token
      line - line content
      after - position after

    • isGenericBeforeCtor

      private static boolean isGenericBeforeCtor(DetailAST ast)
      Checks if generic is before constructor invocation.
      Parameters:
      ast - ast
      Returns:
      true if generic before a constructor invocation

    • isGenericBeforeMethod

      private static boolean isGenericBeforeMethod(DetailAST ast)
      Is generic before method reference.
      Parameters:
      ast - ast
      Returns:
      true if generic before a method ref

    • isAfterMethodReference

      private static boolean isAfterMethodReference(DetailAST genericEnd)
      Checks if current generic end ('>') is located after method reference operator.
      Parameters:
      genericEnd - TokenTypes.GENERIC_END
      Returns:
      true if '>' follows after method reference.

    • processStart

      private void processStart(DetailAST ast)
      Checks the token for the start of Generics.
      Parameters:
      ast - the token to check

    • containsWhitespaceBetween

      private static boolean containsWhitespaceBetween(int fromIndex, int toIndex, String line)
      Returns whether the specified string contains only whitespace between specified indices.
      Parameters:
      fromIndex - the index to start the search from. Inclusive
      toIndex - the index to finish the search. Exclusive
      line - the line to check
      Returns:
      whether there are only whitespaces (or nothing)

    • containsWhitespaceBefore

      private static boolean containsWhitespaceBefore(int before, String line)
      Returns whether the specified string contains only whitespace up to specified index.
      Parameters:
      before - the index to start the search from. Inclusive
      line - the index to finish the search. Exclusive
      Returns:
      true if there are only whitespaces, false if there is nothing before or some other characters

    • isCharacterValidAfterGenericEnd

      private static boolean isCharacterValidAfterGenericEnd(char charAfter)
      Checks whether given character is valid to be right after generic ends.
      Parameters:
      charAfter - character to check
      Returns:
      checks if given character is valid