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

Class ExplicitInitializationCheck

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

    Checks if any class or object member is explicitly initialized to default for its type value (null for object references, zero for numeric types and char and false for boolean.

    Rationale: Each instance variable gets initialized twice, to the same value. Java initializes each instance variable to its default value (0 or null) before performing any initialization specified in the code. So there is a minor inefficiency.

    • Property onlyObjectReferences - control whether only explicit initializations made to null for objects should be checked. Type is boolean. Default value is false.

    To configure the check: 

     <module name="ExplicitInitialization"/>

    Example: 

     public class Test {
   private int intField1 = 0; // violation
   private int intField2 = 1;
   private int intField3;

   private char charField1 = '\0'; // violation
   private char charField2 = 'b';
   private char charField3;

   private boolean boolField1 = false; // violation
   private boolean boolField2 = true;
   private boolean boolField3;

   private Obj objField1 = null; // violation
   private Obj objField2 = new Obj();
   private Obj objField3;

   private int arrField1[] = null; // violation
   private int arrField2[] = new int[10];
   private int arrField3[];
 }

    To configure the check so that it only checks for objects that explicitly initialize to null: 

     <module name="ExplicitInitialization">
   <property name="onlyObjectReferences" value="true"/>
 </module>

    Example: 

     public class Test {
   private int intField1 = 0; // ignored
   private int intField2 = 1;
   private int intField3;

   private char charField1 = '\0'; // ignored
   private char charField2 = 'b';
   private char charField3;

   private boolean boolField1 = false; // ignored
   private boolean boolField2 = true;
   private boolean boolField3;

   private Obj objField1 = null; // violation
   private Obj objField2 = new Obj();
   private Obj objField3;

   private int arrField1[] = null; // violation
   private int arrField2[] = new int[10];
   private int arrField3[];
 }

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • explicit.init
    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

      • ExplicitInitializationCheck

        public ExplicitInitializationCheck()

    • Method Detail

      • getDefaultTokens

        public final 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

      • getRequiredTokens

        public final 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

      • getAcceptableTokens

        public final 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

      • setOnlyObjectReferences

        public void setOnlyObjectReferences​(boolean onlyObjectReferences)
        Setter to control whether only explicit initializations made to null for objects should be checked.
        Parameters:
        onlyObjectReferences - whether only explicit initialization made to null should be checked