Package org.apache.commons.lang3

Class ClassUtils

  • public class ClassUtils
extends Object

    Operates on classes without using reflection.

    This class handles invalid null inputs as best it can. Each method documents its behaviour in more detail.

    The notion of a canonical name includes the human readable name for the type, for example int[]. The non-canonical method variants work with the JVM names, such as [I.

    Since:
    2.0

    • Field Detail

      • PACKAGE_SEPARATOR_CHAR

        public static final char PACKAGE_SEPARATOR_CHAR
        The package separator character: '.' == 46.
        See Also:
        Constant Field Values

      • PACKAGE_SEPARATOR

        public static final String PACKAGE_SEPARATOR
        The package separator String: ".".

      • INNER_CLASS_SEPARATOR_CHAR

        public static final char INNER_CLASS_SEPARATOR_CHAR
        The inner class separator character: '$' == 36.
        See Also:
        Constant Field Values

      • INNER_CLASS_SEPARATOR

        public static final String INNER_CLASS_SEPARATOR
        The inner class separator String: "$".

    • Constructor Detail

      • ClassUtils

        public ClassUtils()

        ClassUtils instances should NOT be constructed in standard programming. Instead, the class should be used as ClassUtils.getShortClassName(cls).

        This constructor is public to permit tools that require a JavaBean instance to operate.

    • Method Detail

      • getShortClassName

        public static String getShortClassName​(Object object,
                                       String valueIfNull)

        Gets the class name minus the package name for an Object.

        Parameters:
        object - the class to get the short name for, may be null
        valueIfNull - the value to return if null
        Returns:
        the class name of the object without the package name, or the null value

      • getShortClassName

        public static String getShortClassName​(Class<?> cls)

        Gets the class name minus the package name from a Class.

        Consider using the Java 5 API Class.getSimpleName() instead. The one known difference is that this code will return "Map.Entry" while the java.lang.Class variant will simply return "Entry".

        Parameters:
        cls - the class to get the short name for.
        Returns:
        the class name without the package name or an empty string

      • getShortClassName

        public static String getShortClassName​(String className)

        Gets the class name minus the package name from a String.

        The string passed in is assumed to be a class name - it is not checked.

        Note that this method differs from Class.getSimpleName() in that this will return "Map.Entry" whilst the java.lang.Class variant will simply return "Entry".

        Parameters:
        className - the className to get the short name for
        Returns:
        the class name of the class without the package name or an empty string

      • getSimpleName

        public static String getSimpleName​(Class<?> cls)

        Null-safe version of aClass.getSimpleName()

        Parameters:
        cls - the class for which to get the simple name; may be null
        Returns:
        the simple class name.
        Since:
        3.0
        See Also:
        Class.getSimpleName()

      • getSimpleName

        public static String getSimpleName​(Class<?> cls,
                                   String valueIfNull)

        Null-safe version of aClass.getSimpleName()

        Parameters:
        cls - the class for which to get the simple name; may be null
        valueIfNull - the value to return if null
        Returns:
        the simple class name or valueIfNull
        Since:
        3.0
        See Also:
        Class.getSimpleName()

      • getSimpleName

        public static String getSimpleName​(Object object)

        Null-safe version of aClass.getSimpleName()

        Parameters:
        object - the object for which to get the simple class name; may be null
        Returns:
        the simple class name or the empty String
        Since:
        3.7
        See Also:
        Class.getSimpleName()

      • getSimpleName

        public static String getSimpleName​(Object object,
                                   String valueIfNull)

        Null-safe version of aClass.getSimpleName()

        Parameters:
        object - the object for which to get the simple class name; may be null
        valueIfNull - the value to return if object is null
        Returns:
        the simple class name or valueIfNull
        Since:
        3.0
        See Also:
        Class.getSimpleName()

      • getName

        public static String getName​(Class<?> cls)

        Null-safe version of Class.getName()

        Parameters:
        cls - the class for which to get the class name; may be null
        Returns:
        the class name or the empty String.
        Since:
        3.7
        See Also:
        Class.getSimpleName()

      • getName

        public static String getName​(Class<?> cls,
                             String valueIfNull)

        Null-safe version of aClass.getName()

        Parameters:
        cls - the class for which to get the class name; may be null
        valueIfNull - the return value if cls is null
        Returns:
        the class name or valueIfNull
        Since:
        3.7
        See Also:
        Class.getName()

      • getName

        public static String getName​(Object object)

        Null-safe version of Class.getName()

        Parameters:
        object - the object for which to get the class name; may be null
        Returns:
        the class name or the empty String
        Since:
        3.7
        See Also:
        Class.getSimpleName()

      • getName

        public static String getName​(Object object,
                             String valueIfNull)

        Null-safe version of aClass.getSimpleName()

        Parameters:
        object - the object for which to get the class name; may be null
        valueIfNull - the value to return if object is null
        Returns:
        the class name or valueIfNull
        Since:
        3.0
        See Also:
        Class.getName()

      • getPackageName

        public static String getPackageName​(Object object,
                                    String valueIfNull)

        Gets the package name of an Object.

        Parameters:
        object - the class to get the package name for, may be null
        valueIfNull - the value to return if null
        Returns:
        the package name of the object, or the null value

      • getPackageName

        public static String getPackageName​(Class<?> cls)

        Gets the package name of a Class.

        Parameters:
        cls - the class to get the package name for, may be null.
        Returns:
        the package name or an empty string

      • getPackageName

        public static String getPackageName​(String className)

        Gets the package name from a String.

        The string passed in is assumed to be a class name - it is not checked.

        If the class is unpackaged, return an empty string.

        Parameters:
        className - the className to get the package name for, may be null
        Returns:
        the package name or an empty string

      • getAbbreviatedName

        public static String getAbbreviatedName​(Class<?> cls,
                                        int len)

        Gets the abbreviated name of a Class.

        Parameters:
        cls - the class to get the abbreviated name for, may be null
        len - the desired length of the abbreviated name
        Returns:
        the abbreviated name or an empty string
        Throws:
        IllegalArgumentException - if len <= 0
        Since:
        3.4
        See Also:
        getAbbreviatedName(String, int)

      • getAbbreviatedName

        public static String getAbbreviatedName​(String className,
                                        int len)

        Gets the abbreviated class name from a String.

        The string passed in is assumed to be a class name - it is not checked.

        The abbreviation algorithm will shorten the class name, usually without significant loss of meaning.

        The abbreviated class name will always include the complete package hierarchy. If enough space is available, rightmost sub-packages will be displayed in full length.

        Examples
        classNamelenreturn
        null 1""
        "java.lang.String" 5"j.l.String"
        "java.lang.String"15"j.lang.String"
        "java.lang.String"30"java.lang.String"
        Parameters:
        className - the className to get the abbreviated name for, may be null
        len - the desired length of the abbreviated name
        Returns:
        the abbreviated name or an empty string
        Throws:
        IllegalArgumentException - if len <= 0
        Since:
        3.4

      • getAllSuperclasses

        public static List<Class<?>> getAllSuperclasses​(Class<?> cls)

        Gets a List of superclasses for the given class.

        Parameters:
        cls - the class to look up, may be null
        Returns:
        the List of superclasses in order going up from this one null if null input

      • getAllInterfaces

        public static List<Class<?>> getAllInterfaces​(Class<?> cls)

        Gets a List of all interfaces implemented by the given class and its superclasses.

        The order is determined by looking through each interface in turn as declared in the source file and following its hierarchy up. Then each superclass is considered in the same way. Later duplicates are ignored, so the order is maintained.

        Parameters:
        cls - the class to look up, may be null
        Returns:
        the List of interfaces in order, null if null input

      • convertClassNamesToClasses

        public static List<Class<?>> convertClassNamesToClasses​(List<String> classNames)

        Given a List of class names, this method converts them into classes.

        A new List is returned. If the class name cannot be found, null is stored in the List. If the class name in the List is null, null is stored in the output List.

        Parameters:
        classNames - the classNames to change
        Returns:
        a List of Class objects corresponding to the class names, null if null input
        Throws:
        ClassCastException - if classNames contains a non String entry

      • convertClassesToClassNames

        public static List<String> convertClassesToClassNames​(List<Class<?>> classes)

        Given a List of Class objects, this method converts them into class names.

        A new List is returned. null objects will be copied into the returned list as null.

        Parameters:
        classes - the classes to change
        Returns:
        a List of class names corresponding to the Class objects, null if null input
        Throws:
        ClassCastException - if classes contains a non-Class entry

      • isAssignable

        public static boolean isAssignable​(Class<?>[] classArray,
                                   Class<?>... toClassArray)

        Checks if an array of Classes can be assigned to another array of Classes.

        This method calls isAssignable for each Class pair in the input arrays. It can be used to check if a set of arguments (the first parameter) are suitably compatible with a set of method parameter types (the second parameter).

        Unlike the Class.isAssignableFrom(java.lang.Class) method, this method takes into account widenings of primitive classes and nulls.

        Primitive widenings allow an int to be assigned to a long, float or double. This method returns the correct result for these cases.

        Null may be assigned to any reference type. This method will return true if null is passed in and the toClass is non-primitive.

        Specifically, this method tests whether the type represented by the specified Class parameter can be converted to the type represented by this Class object via an identity conversion widening primitive or widening reference conversion. See The Java Language Specification, sections 5.1.1, 5.1.2 and 5.1.4 for details.

        Since Lang 3.0, this method will default behavior for calculating assignability between primitive and wrapper types corresponding to the running Java version; i.e. autoboxing will be the default behavior in VMs running Java versions > 1.5.

        Parameters:
        classArray - the array of Classes to check, may be null
        toClassArray - the array of Classes to try to assign into, may be null
        Returns:
        true if assignment possible

      • isAssignable

        public static boolean isAssignable​(Class<?>[] classArray,
                                   Class<?>[] toClassArray,
                                   boolean autoboxing)

        Checks if an array of Classes can be assigned to another array of Classes.

        This method calls isAssignable for each Class pair in the input arrays. It can be used to check if a set of arguments (the first parameter) are suitably compatible with a set of method parameter types (the second parameter).

        Unlike the Class.isAssignableFrom(java.lang.Class) method, this method takes into account widenings of primitive classes and nulls.

        Primitive widenings allow an int to be assigned to a long, float or double. This method returns the correct result for these cases.

        Null may be assigned to any reference type. This method will return true if null is passed in and the toClass is non-primitive.

        Specifically, this method tests whether the type represented by the specified Class parameter can be converted to the type represented by this Class object via an identity conversion widening primitive or widening reference conversion. See The Java Language Specification, sections 5.1.1, 5.1.2 and 5.1.4 for details.

        Parameters:
        classArray - the array of Classes to check, may be null
        toClassArray - the array of Classes to try to assign into, may be null
        autoboxing - whether to use implicit autoboxing/unboxing between primitives and wrappers
        Returns:
        true if assignment possible

      • isAssignable

        public static boolean isAssignable​(Class<?> cls,
                                   Class<?> toClass)

        Checks if one Class can be assigned to a variable of another Class.

        Unlike the Class.isAssignableFrom(java.lang.Class) method, this method takes into account widenings of primitive classes and nulls.

        Primitive widenings allow an int to be assigned to a long, float or double. This method returns the correct result for these cases.

        Null may be assigned to any reference type. This method will return true if null is passed in and the toClass is non-primitive.

        Specifically, this method tests whether the type represented by the specified Class parameter can be converted to the type represented by this Class object via an identity conversion widening primitive or widening reference conversion. See The Java Language Specification, sections 5.1.1, 5.1.2 and 5.1.4 for details.

        Since Lang 3.0, this method will default behavior for calculating assignability between primitive and wrapper types corresponding to the running Java version; i.e. autoboxing will be the default behavior in VMs running Java versions > 1.5.

        Parameters:
        cls - the Class to check, may be null
        toClass - the Class to try to assign into, returns false if null
        Returns:
        true if assignment possible

      • isAssignable

        public static boolean isAssignable​(Class<?> cls,
                                   Class<?> toClass,
                                   boolean autoboxing)

        Checks if one Class can be assigned to a variable of another Class.

        Unlike the Class.isAssignableFrom(java.lang.Class) method, this method takes into account widenings of primitive classes and nulls.

        Primitive widenings allow an int to be assigned to a long, float or double. This method returns the correct result for these cases.

        Null may be assigned to any reference type. This method will return true if null is passed in and the toClass is non-primitive.

        Specifically, this method tests whether the type represented by the specified Class parameter can be converted to the type represented by this Class object via an identity conversion widening primitive or widening reference conversion. See The Java Language Specification, sections 5.1.1, 5.1.2 and 5.1.4 for details.

        Parameters:
        cls - the Class to check, may be null
        toClass - the Class to try to assign into, returns false if null
        autoboxing - whether to use implicit autoboxing/unboxing between primitives and wrappers
        Returns:
        true if assignment possible

      • primitiveToWrapper

        public static Class<?> primitiveToWrapper​(Class<?> cls)

        Converts the specified primitive Class object to its corresponding wrapper Class object.

        NOTE: From v2.2, this method handles Void.TYPE, returning Void.TYPE.

        Parameters:
        cls - the class to convert, may be null
        Returns:
        the wrapper class for cls or cls if cls is not a primitive. null if null input.
        Since:
        2.1

      • primitivesToWrappers

        public static Class<?>[] primitivesToWrappers​(Class<?>... classes)

        Converts the specified array of primitive Class objects to an array of its corresponding wrapper Class objects.

        Parameters:
        classes - the class array to convert, may be null or empty
        Returns:
        an array which contains for each given class, the wrapper class or the original class if class is not a primitive. null if null input. Empty array if an empty array passed in.
        Since:
        2.1

      • wrapperToPrimitive

        public static Class<?> wrapperToPrimitive​(Class<?> cls)

        Converts the specified wrapper class to its corresponding primitive class.

        This method is the counter part of primitiveToWrapper(). If the passed in class is a wrapper class for a primitive type, this primitive type will be returned (e.g. Integer.TYPE for Integer.class). For other classes, or if the parameter is null, the return value is null.

        Parameters:
        cls - the class to convert, may be null
        Returns:
        the corresponding primitive type if cls is a wrapper class, null otherwise
        Since:
        2.4
        See Also:
        primitiveToWrapper(Class)

      • wrappersToPrimitives

        public static Class<?>[] wrappersToPrimitives​(Class<?>... classes)

        Converts the specified array of wrapper Class objects to an array of its corresponding primitive Class objects.

        This method invokes wrapperToPrimitive() for each element of the passed in array.

        Parameters:
        classes - the class array to convert, may be null or empty
        Returns:
        an array which contains for each given class, the primitive class or null if the original class is not a wrapper class. null if null input. Empty array if an empty array passed in.
        Since:
        2.4
        See Also:
        wrapperToPrimitive(Class)

      • isInnerClass

        public static boolean isInnerClass​(Class<?> cls)

        Is the specified class an inner class or static nested class.

        Parameters:
        cls - the class to check, may be null
        Returns:
        true if the class is an inner or static nested class, false if not or null

      • getClass

        public static Class<?> getClass​(ClassLoader classLoader,
                                String className,
                                boolean initialize)
                         throws ClassNotFoundException
        Returns the class represented by className using the classLoader. This implementation supports the syntaxes "java.util.Map.Entry[]", "java.util.Map$Entry[]", "[Ljava.util.Map.Entry;", and "[Ljava.util.Map$Entry;".
        Parameters:
        classLoader - the class loader to use to load the class
        className - the class name
        initialize - whether the class must be initialized
        Returns:
        the class represented by className using the classLoader
        Throws:
        ClassNotFoundException - if the class is not found

      • getClass

        public static Class<?> getClass​(ClassLoader classLoader,
                                String className)
                         throws ClassNotFoundException
        Returns the (initialized) class represented by className using the classLoader. This implementation supports the syntaxes "java.util.Map.Entry[]", "java.util.Map$Entry[]", "[Ljava.util.Map.Entry;", and "[Ljava.util.Map$Entry;".
        Parameters:
        classLoader - the class loader to use to load the class
        className - the class name
        Returns:
        the class represented by className using the classLoader
        Throws:
        ClassNotFoundException - if the class is not found

      • getClass

        public static Class<?> getClass​(String className)
                         throws ClassNotFoundException
        Returns the (initialized) class represented by className using the current thread's context class loader. This implementation supports the syntaxes "java.util.Map.Entry[]", "java.util.Map$Entry[]", "[Ljava.util.Map.Entry;", and "[Ljava.util.Map$Entry;".
        Parameters:
        className - the class name
        Returns:
        the class represented by className using the current thread's context class loader
        Throws:
        ClassNotFoundException - if the class is not found

      • getClass

        public static Class<?> getClass​(String className,
                                boolean initialize)
                         throws ClassNotFoundException
        Returns the class represented by className using the current thread's context class loader. This implementation supports the syntaxes "java.util.Map.Entry[]", "java.util.Map$Entry[]", "[Ljava.util.Map.Entry;", and "[Ljava.util.Map$Entry;".
        Parameters:
        className - the class name
        initialize - whether the class must be initialized
        Returns:
        the class represented by className using the current thread's context class loader
        Throws:
        ClassNotFoundException - if the class is not found

      • getPublicMethod

        public static Method getPublicMethod​(Class<?> cls,
                                     String methodName,
                                     Class<?>... parameterTypes)
                              throws NoSuchMethodException

        Returns the desired Method much like Class.getMethod, however it ensures that the returned Method is from a public class or interface and not from an anonymous inner class. This means that the Method is invokable and doesn't fall foul of Java bug 4071957).

          Set set = Collections.unmodifiableSet(...);
  Method method = ClassUtils.getPublicMethod(set.getClass(), "isEmpty",  new Class[0]);
  Object result = method.invoke(set, new Object[]);
        Parameters:
        cls - the class to check, not null
        methodName - the name of the method
        parameterTypes - the list of parameters
        Returns:
        the method
        Throws:
        NullPointerException - if the class is null
        SecurityException - if a security violation occurred
        NoSuchMethodException - if the method is not found in the given class or if the method doesn't conform with the requirements

      • toClass

        public static Class<?>[] toClass​(Object... array)

        Converts an array of Object in to an array of Class objects. If any of these objects is null, a null element will be inserted into the array.

        This method returns null for a null input array.

        Parameters:
        array - an Object array
        Returns:
        a Class array, null if null array input
        Since:
        2.4

      • getShortCanonicalName

        public static String getShortCanonicalName​(Object object,
                                           String valueIfNull)

        Gets the canonical name minus the package name for an Object.

        Parameters:
        object - the class to get the short name for, may be null
        valueIfNull - the value to return if null
        Returns:
        the canonical name of the object without the package name, or the null value
        Since:
        2.4

      • getCanonicalName

        public static String getCanonicalName​(Class<?> cls)

        Gets the canonical class name for a Class.

        Parameters:
        cls - the class for which to get the canonical class name; may be null
        Returns:
        the canonical name of the class, or the empty String
        Since:
        3.7
        See Also:
        Class.getCanonicalName()

      • getCanonicalName

        public static String getCanonicalName​(Class<?> cls,
                                      String valueIfNull)

        Gets the canonical name for a Class.

        Parameters:
        cls - the class for which to get the canonical class name; may be null
        valueIfNull - the return value if null
        Returns:
        the canonical name of the class, or valueIfNull
        Since:
        3.7
        See Also:
        Class.getCanonicalName()

      • getCanonicalName

        public static String getCanonicalName​(Object object)

        Gets the canonical name for an Object.

        Parameters:
        object - the object for which to get the canonical class name; may be null
        Returns:
        the canonical name of the object, or the empty String
        Since:
        3.7
        See Also:
        Class.getCanonicalName()

      • getCanonicalName

        public static String getCanonicalName​(Object object,
                                      String valueIfNull)

        Gets the canonical name for an Object.

        Parameters:
        object - the object for which to get the canonical class name; may be null
        valueIfNull - the return value if null
        Returns:
        the canonical name of the object or valueIfNull
        Since:
        3.7
        See Also:
        Class.getCanonicalName()

      • getShortCanonicalName

        public static String getShortCanonicalName​(Class<?> cls)

        Gets the canonical name minus the package name from a Class.

        Parameters:
        cls - the class for which to get the short canonical class name; may be null
        Returns:
        the canonical name without the package name or an empty string
        Since:
        2.4

      • getShortCanonicalName

        public static String getShortCanonicalName​(String canonicalName)

        Gets the canonical name minus the package name from a String.

        The string passed in is assumed to be a canonical name - it is not checked.

        Parameters:
        canonicalName - the class name to get the short name for
        Returns:
        the canonical name of the class without the package name or an empty string
        Since:
        2.4

      • getPackageCanonicalName

        public static String getPackageCanonicalName​(Object object,
                                             String valueIfNull)

        Gets the package name from the canonical name of an Object.

        Parameters:
        object - the class to get the package name for, may be null
        valueIfNull - the value to return if null
        Returns:
        the package name of the object, or the null value
        Since:
        2.4

      • getPackageCanonicalName

        public static String getPackageCanonicalName​(Class<?> cls)

        Gets the package name from the canonical name of a Class.

        Parameters:
        cls - the class to get the package name for, may be null.
        Returns:
        the package name or an empty string
        Since:
        2.4

      • getPackageCanonicalName

        public static String getPackageCanonicalName​(String canonicalName)

        Gets the package name from the canonical name.

        The string passed in is assumed to be a canonical name - it is not checked.

        If the class is unpackaged, return an empty string.

        Parameters:
        canonicalName - the canonical name to get the package name for, may be null
        Returns:
        the package name or an empty string
        Since:
        2.4

      • hierarchy

        public static Iterable<Class<?>> hierarchy​(Class<?> type)
        Get an Iterable that can iterate over a class hierarchy in ascending (subclass to superclass) order, excluding interfaces.
        Parameters:
        type - the type to get the class hierarchy from
        Returns:
        Iterable an Iterable over the class hierarchy of the given class
        Since:
        3.2

      • hierarchy

        public static Iterable<Class<?>> hierarchy​(Class<?> type,
                                           ClassUtils.Interfaces interfacesBehavior)
        Get an Iterable that can iterate over a class hierarchy in ascending (subclass to superclass) order.
        Parameters:
        type - the type to get the class hierarchy from
        interfacesBehavior - switch indicating whether to include or exclude interfaces
        Returns:
        Iterable an Iterable over the class hierarchy of the given class
        Since:
        3.2