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.

    To configure the check: 

     <module name="UnnecessaryParentheses"/>

    Which results in the following violations: 

     public int square(int a, int b){
   int square = (a * b); //violation
   return (square); //violation
 }
 int sumOfSquares = 0;
 for(int i=(0); i<10; i++){ //violation
   int x = (i + 1); //violation
   sumOfSquares += (square(x * x)); //violation
 }
 double num = (10.0); //violation
 List<String> list = Arrays.asList("a1", "b1", "c1");
 myList.stream()
   .filter((s) -> s.startsWith("c")) //violation
   .forEach(System.out::println);

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • unnecessary.paren.assign
    • unnecessary.paren.expr
    • unnecessary.paren.ident
    • unnecessary.paren.lambda
    • unnecessary.paren.literal
    • unnecessary.paren.return
    • unnecessary.paren.string
    Since:
    3.4

    • 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

      • MSG_LAMBDA

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

    • 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