Class 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
    • Method Detail

      • 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:
        TokenTypes
      • 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
      • 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,
                                           int[] line,
                                           int after)
        Process Nested generics.
        Parameters:
        ast - token
        line - unicode code points array of line
        after - position after
      • processSingleGeneric

        private void processSingleGeneric​(DetailAST ast,
                                          int[] line,
                                          int after)
        Process Single-generic.
        Parameters:
        ast - token
        line - unicode code points array of line
        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
      • 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,
                                                         int... 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 unicode code points array of line to check
        Returns:
        whether there are only whitespaces (or nothing)
      • containsWhitespaceBefore

        private static boolean containsWhitespaceBefore​(int before,
                                                        int... line)
        Returns whether the specified string contains only whitespace up to specified index.
        Parameters:
        before - the index to finish the search. Exclusive
        line - the unicode code points array of line to check
        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