org.apache.commons.lang
Class ClassUtils

java.lang.Object
  org.apache.commons.lang.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.

Since:

2.0

Version:

$Id: ClassUtils.java 437554 2006-08-28 06:21:41Z bayard $

Author:

Stephen Colebourne, Gary Gregory, Norm Deane, Alban Peignier

Field Summary

static String	INNER_CLASS_SEPARATOR The inner class separator String: "$".
static char	INNER_CLASS_SEPARATOR_CHAR The inner class separator character: '$' == 36.
static String	PACKAGE_SEPARATOR The package separator String: ".".
static char	PACKAGE_SEPARATOR_CHAR The package separator character: '.' == 46.

Constructor Summary

ClassUtils()
ClassUtils instances should NOT be constructed in standard programming.

Method Summary

static List	convertClassesToClassNames(List classes) Given a List of Class objects, this method converts them into class names.
static List	convertClassNamesToClasses(List classNames) Given a List of class names, this method converts them into classes.
static List	getAllInterfaces(Class cls) Gets a List of all interfaces implemented by the given class and its superclasses.
static List	getAllSuperclasses(Class cls) Gets a List of superclasses for the given class.
static Class	getClass(ClassLoader classLoader, String className) Returns the (initialized) class represented by className using the classLoader.
static Class	getClass(ClassLoader classLoader, String className, boolean initialize) Returns the class represented by className using the classLoader.
static Class	getClass(String className) Returns the (initialized )class represented by className using the current thread's context class loader.
static Class	getClass(String className, boolean initialize) Returns the class represented by className using the current thread's context class loader.
static String	getPackageName(Class cls) Gets the package name of a Class.
static String	getPackageName(Object object, String valueIfNull) Gets the package name of an Object.
static String	getPackageName(String className) Gets the package name from a String.
static Method	getPublicMethod(Class cls, String methodName, Class[] parameterTypes) 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.
static String	getShortClassName(Class cls) Gets the class name minus the package name from a Class.
static String	getShortClassName(Object object, String valueIfNull) Gets the class name minus the package name for an Object.
static String	getShortClassName(String className) Gets the class name minus the package name from a String.
static boolean	isAssignable(Class[] classArray, Class[] toClassArray) Checks if an array of Classes can be assigned to another array of Classes.
static boolean	isAssignable(Class cls, Class toClass) Checks if one Class can be assigned to a variable of another Class.
static boolean	isInnerClass(Class cls) Is the specified class an inner class or static nested class.
static Class[]	primitivesToWrappers(Class[] classes) Converts the specified array of primitive Class objects to an array of its corresponding wrapper Class objects.
static Class	primitiveToWrapper(Class cls) Converts the specified primitive Class object to its corresponding wrapper Class object.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

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.

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.

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

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

getAllSuperclasses

public static List 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 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 convertClassNamesToClasses(List 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 convertClassesToClassNames(List 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.

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 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.

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

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

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 names like "java.lang.String[]" as well as "[Ljava.lang.String;".

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 names like "java.lang.String[]" as well as "[Ljava.lang.String;".

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 names like "java.lang.String[]" as well as "[Ljava.lang.String;".

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 names like "java.lang.String[]" as well as "[Ljava.lang.String;".

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 SecurityException,
                                     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 a security violation occured

NoSuchMethodException - if the method is not found in the given class or if the metothod doen't conform with the requirements