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