Package com.puppycrawl.tools.checkstyle.checks.coding

Class UnnecessaryParenthesesCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable
    public class UnnecessaryParenthesesCheck
extends AbstractCheck

    Checks if unnecessary parentheses are used in a statement or expression. The check will flag the following with warnings: 

         return (x);          // parens around identifier
     return (x + 1);      // parens around return value
     int x = (y / 2 + 1); // parens around assignment rhs
     for (int i = (0); i < 10; i++) {  // parens around literal
     t -= (z + 1);        // parens around assignment rhs

    The check is not "type aware", that is to say, it can't tell if parentheses are unnecessary based on the types in an expression. It also doesn't know about operator precedence and associativity; therefore it won't catch something like 

         int x = (a + b) + c;

    In the above case, given that a, b, and c are all int variables, the parentheses around a + b are not needed.

    • Field Detail

      • MSG_IDENT

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

      • MSG_ASSIGN

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

      • MSG_EXPR

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

      • MSG_LITERAL

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

      • MSG_STRING

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

      • MSG_RETURN

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

      • MAX_QUOTED_LENGTH

        private static final int MAX_QUOTED_LENGTH
        The maximum string length before we chop the string.
        See Also:
        Constant Field Values

      • LITERALS

        private static final int[] LITERALS
        Token types for literals.

      • ASSIGNMENTS

        private static final int[] ASSIGNMENTS
        Token types for assignment operations.

      • parentToSkip

        private DetailAST parentToSkip
        Used to test if logging a warning in a parent node may be skipped because a warning was already logged on an immediate child node.

      • assignDepth

        private int assignDepth
        Depth of nested assignments. Normally this will be 0 or 1.

    • Constructor Detail

      • UnnecessaryParenthesesCheck

        public UnnecessaryParenthesesCheck()

    • 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

      • leaveToken

        public void leaveToken​(DetailAST ast)
        Description copied from class: AbstractCheck
        Called after all the child nodes have been process.
        Overrides:
        leaveToken in class AbstractCheck
        Parameters:
        ast - the token leaving

      • isSurrounded

        private static boolean isSurrounded​(DetailAST ast)
        Tests if the given DetailAST is surrounded by parentheses. In short, does ast have a previous sibling whose type is TokenTypes.LPAREN and a next sibling whose type is TokenTypes.RPAREN.
        Parameters:
        ast - the DetailAST to check if it is surrounded by parentheses.
        Returns:
        true if ast is surrounded by parentheses.

      • isExprSurrounded

        private static boolean isExprSurrounded​(DetailAST ast)
        Tests if the given expression node is surrounded by parentheses.
        Parameters:
        ast - a DetailAST whose type is TokenTypes.EXPR.
        Returns:
        true if the expression is surrounded by parentheses.

      • isInTokenList

        private static boolean isInTokenList​(int type,
                                     int... tokens)
        Check if the given token type can be found in an array of token types.
        Parameters:
        type - the token type.
        tokens - an array of token types to search.
        Returns:
        true if type was found in tokens.

      • chopString

        private static java.lang.String chopString​(java.lang.String value)
        Returns the specified string chopped to MAX_QUOTED_LENGTH plus an ellipsis (...) if the length of the string exceeds MAX_QUOTED_LENGTH.
        Parameters:
        value - the string to potentially chop.
        Returns:
        the chopped string if string is longer than MAX_QUOTED_LENGTH; otherwise string.