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

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

    • Field Detail

      • MSG_WS_PRECEDED

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

      • MSG_WS_FOLLOWED

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

      • MSG_WS_NOT_PRECEDED

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

      • MSG_WS_ILLEGAL_FOLLOW

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

    • Constructor Detail

      • GenericWhitespaceCheck

        public GenericWhitespaceCheck()

    • Method Detail

      • 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:
        TokenTypes

      • 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

      • 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:
        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