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

Class EqualsAvoidNullCheck

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

    Checks that any combination of String literals is on the left side of an equals() comparison. Also checks for String literals assigned to some field (such as someString.equals(anotherString = "text")).

    Rationale: Calling the equals() method on String literals will avoid a potential NullPointerException. Also, it is pretty common to see null checks right before equals comparisons, which is not necessary in the example below.

    For example, this code: 

     String nullString = null;
 nullString.equals("My_Sweet_String");

    should be refactored to: 

     String nullString = null;
 "My_Sweet_String".equals(nullString);
    • Property ignoreEqualsIgnoreCase - Control whether to ignore String.equalsIgnoreCase(String) invocations. Type is boolean. Default value is false.

    To configure the check: 

     <module name="EqualsAvoidNull"/>

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • equals.avoid.null
    • equalsIgnoreCase.avoid.null
    Since:
    5.0

    • Field Detail

      • MSG_EQUALS_AVOID_NULL

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

      • MSG_EQUALS_IGNORE_CASE_AVOID_NULL

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

    • Constructor Detail

      • EqualsAvoidNullCheck

        public EqualsAvoidNullCheck()

    • 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

      • setIgnoreEqualsIgnoreCase

        public void setIgnoreEqualsIgnoreCase​(boolean newValue)
        Setter to control whether to ignore String.equalsIgnoreCase(String) invocations.
        Parameters:
        newValue - whether to ignore checking String.equalsIgnoreCase(String).

      • 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

      • 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

      • finishTree

        public void finishTree​(DetailAST ast)
        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:
        ast - the root of the tree