Class IllegalTypeCheck

  • All Implemented Interfaces:
    Configurable, Contextualizable

    public final class IllegalTypeCheck
    extends AbstractCheck

    Checks that particular classes or interfaces are never used.

    Rationale: Helps reduce coupling on concrete classes.

    For additional restriction of type usage see also: IllegalInstantiation, IllegalImport

    It is possible to set illegal class names via short or canonical name. Specifying illegal type invokes analyzing imports and Check puts violations at corresponding declarations (of variables, methods or parameters). This helps to avoid ambiguous cases, e.g.: java.awt.List was set as illegal class name, then, code like:

     import java.util.List;
     ...
     List list; //No violation here
     

    will be ok.

    In most cases it's justified to put following classes to illegalClassNames:

    • GregorianCalendar
    • Hashtable
    • ArrayList
    • LinkedList
    • Vector

    as methods that are differ from interface methods are rarely used, so in most cases user will benefit from checking for them.

    • Property validateAbstractClassNames - Control whether to validate abstract class names. Type is boolean. Default value is false.
    • Property illegalClassNames - Specify classes that should not be used as types in variable declarations, return values or parameters. Type is java.lang.String[]. Default value is HashMap, HashSet, LinkedHashMap, LinkedHashSet, TreeMap, TreeSet, java.util.HashMap, java.util.HashSet, java.util.LinkedHashMap, java.util.LinkedHashSet, java.util.TreeMap, java.util.TreeSet.
    • Property legalAbstractClassNames - Define abstract classes that may be used as types. Type is java.lang.String[]. Default value is "".
    • Property ignoredMethodNames - Specify methods that should not be checked. Type is java.lang.String[]. Default value is getEnvironment, getInitialContext.
    • Property illegalAbstractClassNameFormat - Specify RegExp for illegal abstract class names. Type is java.util.regex.Pattern. Default value is "^(.*[.])?Abstract.*$".
    • Property memberModifiers - Control whether to check only methods and fields with any of the specified modifiers. This property does not affect method calls nor method references nor record components. Type is java.lang.String[]. Validation type is tokenTypesSet. Default value is "".
    • Property tokens - tokens to check Type is java.lang.String[]. Validation type is tokenSet. Default value is: ANNOTATION_FIELD_DEF, CLASS_DEF, INTERFACE_DEF, METHOD_CALL, METHOD_DEF, METHOD_REF, PARAMETER_DEF, VARIABLE_DEF, PATTERN_VARIABLE_DEF, RECORD_DEF, RECORD_COMPONENT_DEF.

    To configure the default check:

     <module name="IllegalType"/>
     
     public class Test extends TreeSet { // violation
       public <T extends java.util.HashSet> void method() { // violation
    
         LinkedHashMap<Integer, String> lhmap =
         new LinkedHashMap<Integer, String>(); // violation
         TreeMap<Integer, String> treemap =
         new TreeMap<Integer, String>(); // violation
         Test t; // OK
         HashMap<String, String> hmap; // violation
         Queue<Integer> intqueue; // OK
    
         java.lang.IllegalArgumentException illegalex; // OK
         java.util.TreeSet treeset; // violation
       }
    
     }
     

    To configure the Check so that particular tokens are checked:

     <module name="IllegalType">
       <property name="tokens" value="METHOD_DEF"/>
     </module>
     
     public class Test extends TreeSet { // OK
       public <T extends java.util.HashSet> void method() { // violation
         LinkedHashMap<Integer, String> lhmap =
         new LinkedHashMap<Integer, String>(); // OK
    
         java.lang.IllegalArgumentException illegalex; // OK
         java.util.TreeSet treeset; // Ok
       }
    
       public <T extends java.util.HashSet> void typeParam(T t) {} // violation
    
       public void fullName(TreeSet a) {} // OK
    
     }
     

    To configure the Check so that it ignores function() methods:

     <module name="IllegalType">
       <property name="ignoredMethodNames" value="function"/>
     </module>
     
     public class Test {
       public HashMap<String, String> function() { // OK
         // code
       }
    
       public HashMap<String, String> function1() { // violation
         // code
       }
     }
     

    To configure the Check so that it validates abstract class names:

      <module name="IllegalType">
        <property name="validateAbstractClassNames" value="true"/>
        <property name="illegalAbstractClassNameFormat" value="Gitt"/>
      </module>
     
     class Test extends Gitter { // violation
     }
    
     class Test1 extends Github { // OK
     }
     

    To configure the Check so that it verifies only public, protected or static methods and fields:

     <module name="IllegalType">
       <property name="memberModifiers" value="LITERAL_PUBLIC,
        LITERAL_PROTECTED, LITERAL_STATIC"/>
     </module>
     
     public class Test {
       public HashMap<String, String> function1() { // violation
         // code
       }
    
       private HashMap<String, String> function2() { // OK
         // code
       }
    
       protected HashMap<Integer, String> function3() { // violation
         // code
       }
    
       public static TreeMap<Integer, String> function4() { // violation
         // code
       }
    
     }
     

    To configure the check so that it verifies usage of types Boolean and Foo:

     <module name="IllegalType">
               <property name="illegalClassNames" value="Boolean, Foo"/>
     </module>
     
     public class Test {
    
       public Set<Boolean> set; // violation
       public java.util.List<Map<Boolean, Foo>> list; // violation
    
       private void method(List<Foo> list, Boolean value) { // violation
         SomeType.<Boolean>foo(); // violation
         final Consumer<Foo> consumer = Foo<Boolean>::foo; // violation
       }
    
       public <T extends Boolean, U extends Serializable> void typeParam(T a) {} // violation
    
       public void fullName(java.util.ArrayList<? super Boolean> a) {} // violation
    
       public abstract Set<Boolean> shortName(Set<? super Boolean> a); // violation
    
       public Set<? extends Foo> typeArgument() { // violation
         return new TreeSet<Foo<Boolean>>();
       }
    
     }
     

    To configure the check to target fields types only:

     <module name="IllegalType">
       <property name="illegalClassNames" value="java.util.Optional"/>
       <property name="tokens" value="VARIABLE_DEF"/>
       <property name="id" value="IllegalTypeOptionalAsField"/>
     </module>
     <module name="SuppressionXpathSingleFilter">
       <property name="query" value="//METHOD_DEF//*"/>
       <property name="id" value="IllegalTypeOptionalAsField"/>
     </module>
     
     import java.util.Optional;
    
     public class Main {
    
       static int field1 = 4; // OK
       public Optional<String> field2; // violation, usage of type 'Optional' is not allowed
       protected String field3; // OK
       Optional<String> field4; // violation, usage of type 'Optional' is not allowed
       private Optional<String> field5; // violation, usage of type 'Optional' is not allowed
    
       void foo() {
         Optional<String> i; // OK
       }
       public <T extends java.util.Optional> void method(T t) { // OK
         Optional<T> i; // OK
       }
     }
     

    Parent is com.puppycrawl.tools.checkstyle.TreeWalker

    Violation Message Keys:

    • illegal.type
    Since:
    3.2
    • Constructor Detail

      • IllegalTypeCheck

        public IllegalTypeCheck()
        Creates new instance of the check.
    • Method Detail

      • setValidateAbstractClassNames

        public void setValidateAbstractClassNames​(boolean validateAbstractClassNames)
        Setter to control whether to validate abstract class names.
        Parameters:
        validateAbstractClassNames - whether abstract class names must be ignored.
      • 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
      • 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
      • isVerifiable

        private boolean isVerifiable​(DetailAST methodOrVariableDef)
        Checks if current method's return type or variable's type is verifiable according to memberModifiers option.
        Parameters:
        methodOrVariableDef - METHOD_DEF or VARIABLE_DEF ast node.
        Returns:
        true if member is verifiable according to memberModifiers option.
      • isContainVerifiableType

        private boolean isContainVerifiableType​(DetailAST modifiers)
        Checks is modifiers contain verifiable type.
        Parameters:
        modifiers - parent node for all modifiers
        Returns:
        true if method or variable can be verified
      • visitTypeDef

        private void visitTypeDef​(DetailAST typeDef)
        Checks the super type and implemented interfaces of a given type.
        Parameters:
        typeDef - class or interface for check.
      • visitMethodDef

        private void visitMethodDef​(DetailAST methodDef)
        Checks return type of a given method.
        Parameters:
        methodDef - method for check.
      • visitParameterDef

        private void visitParameterDef​(DetailAST parameterDef)
        Checks type of parameters.
        Parameters:
        parameterDef - parameter list for check.
      • visitVariableDef

        private void visitVariableDef​(DetailAST variableDef)
        Checks type of given variable.
        Parameters:
        variableDef - variable to check.
      • visitMethodCallOrRef

        private void visitMethodCallOrRef​(DetailAST methodCallOrRef)
        Checks the type arguments of given method call/reference.
        Parameters:
        methodCallOrRef - method call/reference to check.
      • visitImport

        private void visitImport​(DetailAST importAst)
        Checks imported type (as static and star imports are not supported by Check, only type is in the consideration).
        If this type is illegal due to Check's options - puts violation on it.
        Parameters:
        importAst - Import
      • isStarImport

        private static boolean isStarImport​(DetailAST importAst)
        Checks if current import is star import. E.g.:

        import java.util.*;

        Parameters:
        importAst - Import
        Returns:
        true if it is star import
      • checkClassName

        private void checkClassName​(DetailAST ast)
        Checks type and type arguments/parameters of given method, parameter, variable or method call/reference.
        Parameters:
        ast - node to check.
      • checkIdent

        private void checkIdent​(DetailAST type)
        Checks the identifier of the given type.
        Parameters:
        type - node to check.
      • checkType

        private void checkType​(DetailAST type)
        Checks the given type, its arguments and parameters.
        Parameters:
        type - node to check.
      • checkTypeBounds

        private void checkTypeBounds​(DetailAST type)
        Checks the upper and lower bounds for the given type.
        Parameters:
        type - node to check.
      • checkTypeParameters

        private void checkTypeParameters​(DetailAST node)
        Checks the type parameters of the node.
        Parameters:
        node - node to check.
      • checkTypeArguments

        private void checkTypeArguments​(DetailAST node)
        Checks the type arguments of the node.
        Parameters:
        node - node to check.
      • isMatchingClassName

        private boolean isMatchingClassName​(String className)
        Returns true if given class name is one of illegal classes or else false.
        Parameters:
        className - class name to check.
        Returns:
        true if given class name is one of illegal classes or if it matches to abstract class names pattern.
      • getNextSubTreeNode

        private static DetailAST getNextSubTreeNode​(DetailAST currentNodeAst,
                                                    DetailAST subTreeRootAst)
        Gets the next node of a syntactical tree (child of a current node or sibling of a current node, or sibling of a parent of a current node).
        Parameters:
        currentNodeAst - Current node in considering
        subTreeRootAst - SubTree root
        Returns:
        Current node after bypassing, if current node reached the root of a subtree method returns null
      • isCheckedMethod

        private boolean isCheckedMethod​(DetailAST ast)
        Returns true if method has to be checked or false.
        Parameters:
        ast - method def to check.
        Returns:
        true if we should check this method.
      • setIllegalClassNames

        public void setIllegalClassNames​(String... classNames)
        Setter to specify classes that should not be used as types in variable declarations, return values or parameters.
        Parameters:
        classNames - array of illegal variable types
      • setIgnoredMethodNames

        public void setIgnoredMethodNames​(String... methodNames)
        Setter to specify methods that should not be checked.
        Parameters:
        methodNames - array of ignored method names
      • setLegalAbstractClassNames

        public void setLegalAbstractClassNames​(String... classNames)
        Setter to define abstract classes that may be used as types.
        Parameters:
        classNames - array of legal abstract class names
      • setMemberModifiers

        public void setMemberModifiers​(String modifiers)
        Setter to control whether to check only methods and fields with any of the specified modifiers. This property does not affect method calls nor method references nor record components.
        Parameters:
        modifiers - String contains modifiers.