Package org.djutils.reflection

Class ClassUtil

  • public final class ClassUtil
extends Object
    ClassUtil is a utility class providing assistance for Java Classes.

    Copyright (c) 2002-2023 Delft University of Technology, Jaffalaan 5, 2628 BX Delft, the Netherlands. All rights reserved. See for project information https://djutils.org. The DJUTILS project is distributed under a three-clause BSD-style license, which can be found at https://djutils.org/docs/license.html.

    Author:
    Peter Jacobs, Niels Lang, Alexander Verbraeck

    • Method Detail

      • getAllConstructors

        public static <T> Constructor<T>[] getAllConstructors​(Class<T> clazz)
        Returns all the constructors of a class. Public, package, protected and private constructors are returned. This method returns an array of length 0 if the class object represents an interface, a primitive type, an array class, or void. Note that the constructors of the superclass are not returned as these can never be invoked.
        Type Parameters:
        T - the class of the constructors
        Parameters:
        clazz - Class<T>; the class to resolve the constructors for.
        Returns:
        an array with all constructors

      • resolveConstructor

        public static <T> Constructor<T> resolveConstructor​(Class<T> clazz,
                                                    Class<?> callerClass,
                                                    Class<?>[] parameterTypes)
                                             throws NoSuchMethodException,
                                                    IllegalAccessException
        Returns the constructor of a class with a particular signature if and only if the caller class can invoke that constructor. So a private constructor will not be invoked, unless the caller class is the class that defines the constructor. For a protected class the superclass and classes in the same package can invoke the constructor, but other classes should not be able to invoke the constructor.
        Type Parameters:
        T - the class of the constructor
        Parameters:
        clazz - Class<T>; the class for which the constructor needs to be
        callerClass - Class<?>; the calling class for which the test is carried out whether the constructor is visible
        parameterTypes - Class<?>[]; the parameter types for the constructor's signature
        Returns:
        the retrieved constructor
        Throws:
        NoSuchMethodException - if the constructor with the given signature does not exist
        IllegalAccessException - if the constructor exists but is not callable from the callerClass

      • resolveConstructor

        public static <T> Constructor<T> resolveConstructor​(Class<T> clazz,
                                                    Class<?>[] parameterTypes)
                                             throws NoSuchMethodException
        returns the interface method.
        Type Parameters:
        T - the class of the constructor
        Parameters:
        clazz - Class<T>; the class to start with
        parameterTypes - Class<?>[]; the parameterTypes
        Returns:
        Constructor
        Throws:
        NoSuchMethodException - if the method cannot be resolved

      • resolveConstructor

        public static <T> Constructor<T> resolveConstructor​(Class<T> clazz,
                                                    Object[] arguments)
                                             throws NoSuchMethodException
        returns the constructor.
        Type Parameters:
        T - the class of the constructor
        Parameters:
        clazz - Class<T>; the clazz to start with
        arguments - Object[]; the arguments
        Returns:
        Constructor
        Throws:
        NoSuchMethodException - on lookup failure

      • matchSignature

        public static boolean matchSignature​(Constructor<?> constructor,
                                     Class<?>[] argTypes)
        Filters an array methods for signatures that are compatible with a given signature.
        Parameters:
        constructor - Constructor<?>; which are constructors to be filtered.
        argTypes - Class<?>[]; are the constructor's argument types
        Returns:
        boolean if methodParameters assignable from argTypes

      • matchSignature

        public static <T> Constructor<T>[] matchSignature​(Constructor<T>[] constructors,
                                                  Class<?>[] argTypes)
        Filters an array methods for signatures that are compatible with a given signature.
        Type Parameters:
        T - the class of the constructor
        Parameters:
        constructors - Constructor<T>[]; which are constructors to be filtered.
        argTypes - Class<?>[]; are the constructor's argument types
        Returns:
        Constructor<?>[] An unordered Constructor-array consisting of the elements of 'constructors' that match with the given signature. An array with 0 elements is returned when no matching Method objects are found.

      • getAllFields

        public static Set<Field> getAllFields​(Class<?> clazz,
                                      Set<Field> result)
        gets all the fields of a class (public, protected, package, and private) and adds the result to the return value.
        Parameters:
        clazz - Class<?>; the class
        result - Set<Field>; the resulting set
        Returns:
        the set of fields including all fields of the field clazz

      • getAllFields

        public static Set<Field> getAllFields​(Class<?> clazz)
        gets all the fields of a class (public, protected, package, and private).
        Parameters:
        clazz - Class<?>; the class
        Returns:
        all fields of the class

      • resolveField

        public static Field resolveField​(Class<?> clazz,
                                 String fieldName)
                          throws NoSuchFieldException
        resolves the field for a class, taking into account inner classes.
        Parameters:
        clazz - the class to resolve the field for, including inner classes
        fieldName - name of the field
        Returns:
        Field the field
        Throws:
        NoSuchFieldException - on no such field

      • resolveField

        public static Field resolveField​(Class<?> clazz,
                                 Class<?> callerClass,
                                 String name)
                          throws NoSuchFieldException
        returns the field.
        Parameters:
        clazz - Class<?>; the class to start with
        callerClass - Class<?>; the calling class
        name - String; the fieldName
        Returns:
        Constructor
        Throws:
        NoSuchFieldException - if the method cannot be resolved

      • resolveField

        public static Field resolveField​(Object object,
                                 String fieldName)
                          throws NoSuchFieldException
        resolves the field for a given object instance.
        Parameters:
        object - Object; the object to resolve the field for
        fieldName - String; name of the field to resolve
        Returns:
        the field (if found)
        Throws:
        NoSuchFieldException - if the field cannot be resolved

      • getAllMethods

        public static List<Method> getAllMethods​(Class<?> clazz,
                                         List<Method> result)
        gets all the methods of a class (public, protected, package, and private) and adds the result to the return value.
        Parameters:
        clazz - Class<?>; the class
        result - List<Method>; the resulting set
        Returns:
        the set of methods including all methods of the field clazz

      • getAllMethods

        public static List<Method> getAllMethods​(Class<?> clazz)
        gets all the methods of a class (public, protected, package, and private).
        Parameters:
        clazz - Class<?>; the class
        Returns:
        all methods of the class

      • getAllMethods

        public static List<Method> getAllMethods​(Class<?> clazz,
                                         String name,
                                         List<Method> result)
        gets all the methods of a class (public, protected, package, and private) with a certain name and adds the result to the return value.
        Parameters:
        clazz - Class<?>; the class
        name - String; the name of the method to look up
        result - List<Method>; the resulting set
        Returns:
        the set of methods including all methods with the given name of the field clazz

      • getAllMethods

        public static List<Method> getAllMethods​(Class<?> clazz,
                                         String name)
        gets all the methods of a class (public, protected, package, and private) with a certain name.
        Parameters:
        clazz - Class<?>; the class
        name - String; the name of the method to look up
        Returns:
        all methods of the class with a certain name

      • resolveMethod

        public static Method resolveMethod​(Class<?> clazz,
                                   Class<?> callerClass,
                                   String name,
                                   Class<?>[] parameterTypes)
                            throws NoSuchMethodException
        returns the interface method.
        Parameters:
        clazz - Class<?>; the class to start with
        callerClass - Class<?>; the caller class
        name - String; the name of the method
        parameterTypes - Class<?>[]; the parameterTypes
        Returns:
        Method
        Throws:
        NoSuchMethodException - on lookup failure

      • resolveMethod

        public static Method resolveMethod​(Class<?> clazz,
                                   String name,
                                   Class<?>[] parameterTypes)
                            throws NoSuchMethodException
        returns the interface method.
        Parameters:
        clazz - Class<?>; the class to start with
        name - String; the name of the method
        parameterTypes - Class<?>[]; the parameterTypes
        Returns:
        Method
        Throws:
        NoSuchMethodException - on lookup failure

      • resolveMethod

        public static Method resolveMethod​(Object object,
                                   String name,
                                   Class<?>[] parameterTypes)
                            throws NoSuchMethodException
        resolves a method the method.
        Parameters:
        object - Object; the object to start with
        name - String; the name of the method
        parameterTypes - Class<?>[]; the parameterTypes
        Returns:
        Method
        Throws:
        NoSuchMethodException - on lookup failure

      • resolveMethod

        public static Method resolveMethod​(Object object,
                                   String name,
                                   Object[] arguments)
                            throws NoSuchMethodException
        returns the method.
        Parameters:
        object - Object; the object to start with
        name - String; the name of the method
        arguments - Object[]; the arguments
        Returns:
        Method
        Throws:
        NoSuchMethodException - on lookup failure

      • getAllAnnotations

        public static Set<Annotation> getAllAnnotations​(Class<?> clazz,
                                                Set<Annotation> result)
        gets all the annotations of a class (public, protected, package, and private) and adds the result to the return value.
        Parameters:
        clazz - Class<?>; the class
        result - Set<Annotation>; the resulting set
        Returns:
        the set of annotations including all annotations of the annotation clazz

      • getAllAnnotations

        public static Set<Annotation> getAllAnnotations​(Class<?> clazz)
        gets all the annotations of a class (public, protected, package, and private).
        Parameters:
        clazz - Class<?>; the class
        Returns:
        all annotations of the class

      • resolveAnnotation

        public static Annotation resolveAnnotation​(Class<?> clazz,
                                           Class<? extends Annotation> annotationClass)
                                    throws NoSuchElementException
        resolves the annotation for a class, taking into account inner classes.
        Parameters:
        clazz - the class to resolve the annotation for, including inner classes
        annotationClass - class of the annotation
        Returns:
        Annotation the annotation
        Throws:
        NoSuchElementException - on no such annotation

      • isVisible

        public static boolean isVisible​(int modifiers,
                                Class<?> declaringClass,
                                Class<?> caller)
        Returns whether a declaringClass is accessible according to the modifiers.
        Parameters:
        modifiers - int; the modifiers
        declaringClass - Class<?>; the declaringClass
        caller - Class<?>; the caller
        Returns:
        boolean isVisible

      • isMoreSpecific

        public static boolean isMoreSpecific​(Class<?>[] a,
                                     Class<?>[] b)
        Determines & returns whether constructor 'a' is more specific than constructor 'b', as defined in the Java Language Specification par 15.12.
        Parameters:
        a - Class<?>[]; reflects the first constructor
        b - Class<?>[]; reflects the second constructor
        Returns:
        true if 'a' is more specific than b, false otherwise. 'false' is also returned when constructors are incompatible, e.g. have different names or a different number of parameters.

      • isMoreSpecific

        public static boolean isMoreSpecific​(Constructor<?> a,
                                     Constructor<?> b)
        Determines & returns whether constructor 'a' is more specific than constructor 'b', as defined in the Java Language Specification par 15.12.
        Parameters:
        a - Constructor<?>; the first constructor
        b - Constructor<?>; the second constructor
        Returns:
        true if 'a' is more specific than b, false otherwise. 'false' is also returned when constructors are incompatible, e.g. have different names or a different number of parameters.

      • isMoreSpecific

        public static boolean isMoreSpecific​(Method a,
                                     Method b)
        Determines & returns whether constructor 'a' is more specific than constructor 'b', as defined in the Java Language Specification par 15.12.
        Parameters:
        a - Method; reflects the first method
        b - Method; reflects the second method
        Returns:
        true if 'a' is more specific than b, false otherwise. 'false' is also returned when constructors are incompatible, e.g. have different names or a different number of parameters.

      • isVisible

        public static boolean isVisible​(Field field,
                                Class<?> caller)
        Returns whether a field is visible for a caller.
        Parameters:
        field - Field; The field
        caller - Class<?>; The class of the caller for whom invocation visibility is checked.
        Returns:
        boolean yes or no

      • isVisible

        public static boolean isVisible​(Constructor<?> constructor,
                                Class<?> caller)
        Returns whether a constructor is visible for a caller.
        Parameters:
        constructor - Constructor<?>; The constructor
        caller - Class<?>; The class of the caller for whom invocation visibility is checked.
        Returns:
        boolean yes or no

      • isVisible

        public static boolean isVisible​(Method method,
                                Class<?> caller)
        Returns whether a method is visible for a caller.
        Parameters:
        method - Method; The method
        caller - Class<?>; The class of the caller for whom invocation visibility is checked.
        Returns:
        boolean yes or no

      • matchSignature

        public static List<Method> matchSignature​(List<Method> methods,
                                          String name,
                                          Class<?>[] argTypes)
        Filters an array methods for signatures that are compatible with a given signature.
        Parameters:
        methods - List<Method>; which are methods to be filtered.
        name - String; reflects the method's name, part of the signature
        argTypes - Class<?>[]; are the method's argument types
        Returns:
        Method[] An unordered Method-array consisting of the elements of 'methods' that match with the given signature. An array with 0 elements is returned when no matching Method objects are found.

      • matchSignature

        public static boolean matchSignature​(Method method,
                                     String name,
                                     Class<?>[] argTypes)
        Filters an array methods for signatures that are compatible with a given signature.
        Parameters:
        method - Method; The method to be filtered.
        name - String; reflects the method's name, part of the signature
        argTypes - Class<?>[]; are the method's argument types
        Returns:
        boolean if methodParameters assignable from argTypes

      • getClass

        public static Class<?>[] getClass​(Object[] array)
        Converts an array of objects to their corresponding classes. Note that primitive types are always autoboxed to the corresponding object types. So an int in the array will have an Integer.class at the position in the resulting Class array.
        Parameters:
        array - Object[]; the array to invoke
        Returns:
        Class<?>[] the result;

      • classFileDescriptor

        public static ClassUtil.ClassFileDescriptor classFileDescriptor​(Object object)
        Retrieve a file pointer of a class, e.g. to request the last compilation date.
        Parameters:
        object - Object; the object for which the class information should be retrieved
        Returns:
        a ClassFileDescriptor with some information of the .class file

      • classFileDescriptor

        public static ClassUtil.ClassFileDescriptor classFileDescriptor​(Class<?> clazz)
        Retrieve a file pointer of a class, e.g. to request the last compilation date.
        Parameters:
        clazz - Class<?>; the class for which a file descriptor should be retrieved
        Returns:
        a ClassFileDescriptor with some information of the .class file

      • classFileDescriptor

        public static ClassUtil.ClassFileDescriptor classFileDescriptor​(URL clazzUrl)
        Retrieve a file pointer of a class, e.g. to request the last compilation date.
        Parameters:
        clazzUrl - URL; the URL to a class for which a file descriptor should be retrieved
        Returns:
        a ClassFileDescriptor with some information of the .class file