Class MultipleStringLiteralsCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable

    public class MultipleStringLiteralsCheck
    extends AbstractCheck

    Checks for multiple occurrences of the same string literal within a single file.

    Rationale: Code duplication makes maintenance more difficult, so it can be better to replace the multiple occurrences with a constant.

    • Property allowedDuplicates - Specify the maximum number of occurrences to allow without generating a warning. Type is int. Default value is 1.
    • Property ignoreStringsRegexp - Specify RegExp for ignored strings (with quotation marks). Type is java.util.regex.Pattern. Default value is "^""$".
    • Property ignoreOccurrenceContext - Specify token type names where duplicate strings are ignored even if they don't match ignoredStringsRegexp. This allows you to exclude syntactical contexts like annotations or static initializers from the check. Type is java.lang.String[]. Validation type is tokenTypesSet. Default value is ANNOTATION.

    To configure the check:

     <module name="MultipleStringLiterals"/>
     

    Example:

     public class MyClass {
       String a = "StringContents";
       String a1 = "unchecked";
       @SuppressWarnings("unchecked") // OK, duplicate strings are ignored in annotations
       public void myTest() {
         String a2 = "StringContents"; // violation, "StringContents" occurs twice
         String a3 = "DoubleString" + "DoubleString"; // violation, "DoubleString" occurs twice
         String a4 = "SingleString"; // OK
         String a5 = ", " + ", " + ", "; // violation, ", " occurs three times
       }
     }
     

    To configure the check so that it allows two occurrences of each string:

     <module name="MultipleStringLiterals">
       <property name="allowedDuplicates" value="2"/>
     </module>
     

    Example:

     public class MyClass {
       String a = "StringContents";
       String a1 = "unchecked";
       @SuppressWarnings("unchecked") // OK, duplicate strings are ignored in annotations
       public void myTest() {
         String a2 = "StringContents"; // OK, two occurrences are allowed
         String a3 = "DoubleString" + "DoubleString"; // OK, two occurrences are allowed
         String a4 = "SingleString"; // OK
         String a5 = ", " + ", " + ", "; // violation, three occurrences are NOT allowed
       }
     }
     

    To configure the check so that it ignores ", " and empty strings:

     <module name="MultipleStringLiterals">
       <property name="ignoreStringsRegexp"
         value='^(("")|(", "))$'/>
     </module>
     

    Example:

     public class MyClass {
       String a = "StringContents";
       String a1 = "unchecked";
       @SuppressWarnings("unchecked") // OK, duplicate strings are ignored in annotations
       public void myTest() {
         String a2 = "StringContents"; // violation, "StringContents" occurs twice
         String a3 = "DoubleString" + "DoubleString"; // violation, "DoubleString" occurs twice
         String a4 = "SingleString"; // OK
         String a5 = ", " + ", " + ", "; // OK, multiple occurrences of ", " are allowed
       }
     }
     

    To configure the check so that it flags duplicate strings in all syntactical contexts, even in annotations like @SuppressWarnings("unchecked"):

     <module name="MultipleStringLiterals">
       <property name="ignoreOccurrenceContext" value=""/>
     </module>
     

    Example:

     public class MyClass {
       String a = "StringContents";
       String a1 = "unchecked";
       @SuppressWarnings("unchecked") // violation, "unchecked" occurs twice
       public void myTest() {
         String a2 = "StringContents"; // violation, "StringContents" occurs twice
         String a3 = "DoubleString" + "DoubleString"; // violation, "DoubleString" occurs twice
         String a4 = "SingleString"; // OK
         String a5 = ", " + ", " + ", "; // violation, ", " occurs three times
       }
     }
     

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • multiple.string.literal
    Since:
    3.5
    • Field Detail

      • ALL_NEW_LINES

        private static final Pattern ALL_NEW_LINES
        Compiled pattern for all system newlines.
      • ignoreOccurrenceContext

        private final BitSet ignoreOccurrenceContext
        Specify token type names where duplicate strings are ignored even if they don't match ignoredStringsRegexp. This allows you to exclude syntactical contexts like annotations or static initializers from the check.
      • allowedDuplicates

        private int allowedDuplicates
        Specify the maximum number of occurrences to allow without generating a warning.
    • Method Detail

      • setAllowedDuplicates

        public void setAllowedDuplicates​(int allowedDuplicates)
        Setter to specify the maximum number of occurrences to allow without generating a warning.
        Parameters:
        allowedDuplicates - The maximum number of duplicates.
      • setIgnoreStringsRegexp

        public final void setIgnoreStringsRegexp​(Pattern ignoreStringsRegexp)
        Setter to specify RegExp for ignored strings (with quotation marks).
        Parameters:
        ignoreStringsRegexp - regular expression pattern for ignored strings
      • setIgnoreOccurrenceContext

        public final void setIgnoreOccurrenceContext​(String... strRep)
        Setter to specify token type names where duplicate strings are ignored even if they don't match ignoredStringsRegexp. This allows you to exclude syntactical contexts like annotations or static initializers from the check.
        Parameters:
        strRep - the string representation of the tokens interested in
      • 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
      • finishTree

        public void finishTree​(DetailAST rootAST)
        Description copied from class: AbstractCheck
        Called after finished processing a tree. Ideal place to report on information collected whilst processing a tree.
        Overrides:
        finishTree in class AbstractCheck
        Parameters:
        rootAST - the root of the tree