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 Details

    • MSG_IDENT

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

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

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

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

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

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

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

    • UnnecessaryParenthesesCheck

      public UnnecessaryParenthesesCheck()
  • 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:
    • 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
    • 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