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

Class StringLiteralEqualityCheck

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

    Checks that string literals are not used with == or !=. Since == will compare the object references, not the actual value of the strings, String.equals() should be used. More information can be found in this article.

    Rationale: Novice Java programmers often use code like: 

     if (x == "something")

    when they mean 

     if ("something".equals(x))

    To configure the check: 

     <module name="StringLiteralEquality"/>

    Examples of violations: 

     String status = "pending";

 if (status == "done") {} // violation

 while (status != "done") {} // violation

 boolean flag = (status == "done"); // violation

 boolean flag = (status.equals("done")); // OK

 String name = "X";

 if (name == getName()) {}
 // OK, limitation that check cannot tell runtime type returned from method call

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • string.literal.equality
    Since:
    3.2

    • Field Detail

      • MSG_KEY

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

    • Constructor Detail

      • StringLiteralEqualityCheck

        public StringLiteralEqualityCheck()

    • 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