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

      • onlyObjectReferences

        private boolean onlyObjectReferences
        Control whether only explicit initializations made to null for objects should be checked.
    • Method Detail

      • 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
      • validateNonObjects

        private void validateNonObjects​(DetailAST ast)
        Checks for explicit initializations made to 'false', '0' and '\0'.
        Parameters:
        ast - token being checked for explicit initializations
      • isZeroChar

        private static boolean isZeroChar​(DetailAST exprStart)
        Examine char literal for initializing to default value.
        Parameters:
        exprStart - expression
        Returns:
        true is literal is initialized by zero symbol
      • isSkipCase

        private static boolean isSkipCase​(DetailAST ast)
        Checks for cases that should be skipped: no assignment, local variable, final variables.
        Parameters:
        ast - Variable def AST
        Returns:
        true is that is a case that need to be skipped.
      • isNumericType

        private static boolean isNumericType​(int type)
        Determine if a given type is a numeric type.
        Parameters:
        type - code of the type for check.
        Returns:
        true if it's a numeric type.
        See Also:
        TokenTypes
      • isZero

        private static boolean isZero​(DetailAST expr)
        Checks if given node contains numeric constant for zero.
        Parameters:
        expr - node to check.
        Returns:
        true if given node contains numeric constant for zero.