org.zkoss.lang
Class Classes

java.lang.Object
  org.zkoss.lang.Classes

public class Classes
extends java.lang.Object

Utilities to handle java.lang.Class

Author:

tomyeh

Nested Class Summary

static class

Classes.MethodInfo The method info class used for parseMethod(String signature).

Field Summary

static int	B_GET Search the get method; not imply B_METHODONLY.
static int	B_METHOD_ONLY Only search for methods; excluding fields.
static int	B_PUBLIC_ONLY Only search for public methods or fields.
static int	B_SET Search the set method; not imply B_METHODONLY.

Constructor Summary

Classes()

Method Summary

static java.lang.Object	coerce(java.lang.Class<?> cls, java.lang.Object val) Converts an object to the specified class.
static java.lang.Object	coerce(java.lang.Class<?> cls, java.lang.Object val, boolean nullable) Converts to the specified type.
static boolean	containsMethod(java.lang.Class<?> cls, java.lang.String name, java.lang.Class<?>[] paramTypes) Tests whether a class contains the specified method.
static java.lang.String	correctFieldName(java.lang.String name) Corrects a string to a valid Java name.
static boolean	existsByThread(java.lang.String clsnm) Returns whether the specified class exists for the current thread's context class loader.
static java.lang.Class<?>	forNameByThread(java.lang.String clsName) Returns the Class object of the specified class name, using the current thread's context class loader.
static java.lang.reflect.AccessibleObject	getAccessibleObject(java.lang.Class<?> cls, java.lang.String name, java.lang.Class<?>[] argTypes, int flags) Gets the specified accessible object, either a method or a field, by searching the specified name.
static java.lang.Class<?>[]	getAllInterfaces(java.lang.Class<?> cls) Returns all interfaces that are implemented by the specified class.
static java.lang.reflect.Field	getAnyField(java.lang.Class<?> cls, java.lang.String name) Gets the specified field by searching all fields including any access control and any base class.
static java.lang.reflect.Method	getAnyMethod(java.lang.Class<?> cls, java.lang.String name, java.lang.Class<?>[] argTypes) Gets the specified method by searching all methods including any access control and any base class.
static java.lang.reflect.Method	getCloseMethod(java.lang.Class<?> cls, java.lang.String name, java.lang.Class<?>[] argTypes) Gets one of the close methods -- a close method is a method with the same name and the compatible argument type.
static java.lang.reflect.Method	getCloseMethodBySubclass(java.lang.Class<?> cls, java.lang.String name, java.lang.Class<?>[] argTypes) Like getCloseMethod(java.lang.Class, java.lang.String, java.lang.Class[]) to get a 'close' method, but it look for subclass of the argument (instead of superclass).
static java.lang.reflect.Method[]	getCloseMethods(java.lang.Class<?> cls, java.lang.String name, java.lang.Class<?>[] argTypes) Returns all close methods that match the specified condition, or a zero-length array if none is found.
static java.lang.reflect.Method[]	getCloseMethodsBySubclass(java.lang.Class<?> cls, java.lang.String name, java.lang.Class<?>[] argTypes) Like getCloseMethods(java.lang.Class, java.lang.String, java.lang.Class[]) to get all 'close' methods, but it look for subclass of the argument (instead of superclass).
static java.lang.reflect.Method	getMethodByObject(java.lang.Class<?> cls, java.lang.String name, java.lang.Object[] args) Gets one of the close method by specifying the arguments, rather than the argument types.
static java.lang.reflect.Method	getMethodBySignature(java.lang.Class<?> cls, java.lang.String signature, java.util.Collection<java.lang.String> params) Gets the method based on the signature.
static java.lang.reflect.Method	getMethodBySignature(java.lang.Class<?> cls, java.lang.String signature, java.util.Collection<java.lang.String> params, ClassResolver resolver) Gets the method based on the signature with a class resolver.
static java.lang.reflect.Method	getMethodInPublic(java.lang.Class<?> cls, java.lang.String name, java.lang.Class<?>[] argTypes) Gets the method that is declared in a public class/interface.
static java.lang.Class<?>[]	getSuperClasses(java.lang.Class<?> cls, java.lang.Class<?>[] clsToCheck) Searches thru each element of the specified array of classes, and returns classes that are super-classes (or equal) of the specified class.
static java.lang.Class<?>	getTopmostInterface(java.lang.Class<?> cls, java.lang.Class<?> subIF) Gets the topmost interface of the specified class or interface that implements or extends the specified interface.
static boolean	isAttribute(java.lang.String methodName) Tests if a method name is an attribute, i.e., prefixing with is, get or set.
static boolean	isNumeric(java.lang.Class<?> cls, boolean extend) Checks whether the specified class is a numeric class.
static boolean	isPrimitiveWrapper(java.lang.Class<?> cls) Check whether the specified class is a primitive or a primitive wrapper.
static java.lang.Object	newInstance(java.lang.Class<?> cls, java.lang.Class<?>[] argTypes, java.lang.Object[] args) Instantiates a new instance of the specified class with the specified arguments and argument types.
static java.lang.Object	newInstance(java.lang.Class<?> cls, java.lang.Object[] args) Instantiates a new instance of the specified class with the specified argument.
static java.lang.Object	newInstance(java.lang.String clsName, java.lang.Class<?>[] argTypes, java.lang.Object[] args) Instantiates a new instance of the specified class name with the specified arguments.
static java.lang.Object	newInstanceByThread(java.lang.String clsName) Creates and initializes a new instance of the specified class name with default constructor, by use of forNameByThread(java.lang.String).
static java.lang.Object	newInstanceByThread(java.lang.String clsName, java.lang.Class<?>[] argTypes, java.lang.Object[] args) Creates and initializes a new instance of the specified class name with the specified arguments, by use of forNameByThread(java.lang.String).
static Classes.MethodInfo	parseMethod(java.lang.String signature) Gets the method information from a signature.
static java.lang.String	toAttributeName(java.lang.String methodName) Converts a method name to an attribute name by removing the prefix is, get or set, or null if it doesn't start with is, get or set.
static java.lang.String	toInternalForm(java.lang.String clsName) Change class name to internal form (e.g. byte[] -> [B).
static java.lang.String	toMethodName(java.lang.String attrName, java.lang.String prefix) Convert an attribute name, returned by toAttributeName, to a method name.

Methods inherited from class java.lang.Object

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

Field Detail

B_GET

public static final int B_GET

Search the get method; not imply B_METHODONLY.

See Also:

Constant Field Values

B_SET

public static final int B_SET

Search the set method; not imply B_METHODONLY.

See Also:

Constant Field Values

B_PUBLIC_ONLY

public static final int B_PUBLIC_ONLY

Only search for public methods or fields.

See Also:

Constant Field Values

B_METHOD_ONLY

public static final int B_METHOD_ONLY

Only search for methods; excluding fields.

See Also:

Constant Field Values

Constructor Detail

Classes

public Classes()

Method Detail

newInstance

public static final java.lang.Object newInstance(java.lang.Class<?> cls,
                                                 java.lang.Class<?>[] argTypes,
                                                 java.lang.Object[] args)
                                          throws java.lang.NoSuchMethodException,
                                                 java.lang.InstantiationException,
                                                 java.lang.reflect.InvocationTargetException,
                                                 java.lang.IllegalAccessException

Instantiates a new instance of the specified class with the specified arguments and argument types.

Note only public constructors are searched.

Parameters:

cls - the class of the instance to create

argTypes - the argument types of the constructor to invoke

args - the arguments to initialize the instance

Returns:

the new instance

Throws:

java.lang.NoSuchMethodException - if a matching method is not found

java.lang.InstantiationException - if the class that declares the underlying constructor represents an abstract class

java.lang.reflect.InvocationTargetException - if the underlying constructor throws an exception

java.lang.IllegalAccessException

See Also:

newInstance(String, Class[], Object[])

newInstance

public static final java.lang.Object newInstance(java.lang.Class<?> cls,
                                                 java.lang.Object[] args)
                                          throws java.lang.NoSuchMethodException,
                                                 java.lang.InstantiationException,
                                                 java.lang.reflect.InvocationTargetException,
                                                 java.lang.IllegalAccessException

Instantiates a new instance of the specified class with the specified argument.

It searches all constructors for the first one that matches the specified arguments.

Throws:

java.lang.NoSuchMethodException

java.lang.InstantiationException

java.lang.reflect.InvocationTargetException

java.lang.IllegalAccessException

Since:

3.0.1

newInstance

public static final java.lang.Object newInstance(java.lang.String clsName,
                                                 java.lang.Class<?>[] argTypes,
                                                 java.lang.Object[] args)
                                          throws java.lang.NoSuchMethodException,
                                                 java.lang.InstantiationException,
                                                 java.lang.reflect.InvocationTargetException,
                                                 java.lang.ClassNotFoundException,
                                                 java.lang.IllegalAccessException

Instantiates a new instance of the specified class name with the specified arguments.

It uses Class.forName to get the class.

Parameters:

clsName - the class name of the instance to create

argTypes - the argument types of the constructor to invoke

args - the arguments to initialize the instance

Returns:

the new instance

Throws:

java.lang.NoSuchMethodException - if a matching method is not found

java.lang.InstantiationException - if the class that declares the underlying constructor represents an abstract class

java.lang.reflect.InvocationTargetException - if the underlying constructor throws an exception

java.lang.ClassNotFoundException - if the specified class name is not a class

java.lang.IllegalAccessException

See Also:

newInstance(Class, Class[], Object[])

newInstanceByThread

public static final java.lang.Object newInstanceByThread(java.lang.String clsName,
                                                         java.lang.Class<?>[] argTypes,
                                                         java.lang.Object[] args)
                                                  throws java.lang.NoSuchMethodException,
                                                         java.lang.InstantiationException,
                                                         java.lang.reflect.InvocationTargetException,
                                                         java.lang.ClassNotFoundException,
                                                         java.lang.IllegalAccessException

Creates and initializes a new instance of the specified class name with the specified arguments, by use of forNameByThread(java.lang.String).

It uses forNameByThread(java.lang.String) to get the class.

Parameters:

clsName - the class name of the instance to create

argTypes - the argument types of the constructor to invoke

args - the arguments to initialize the instance

Returns:

the new instance

Throws:

java.lang.NoSuchMethodException - if a matching method is not found

java.lang.InstantiationException - if the class that declares the underlying constructor represents an abstract class

java.lang.reflect.InvocationTargetException - if the underlying constructor throws an exception

java.lang.ClassNotFoundException - if the specified class name is not a class

java.lang.IllegalAccessException

See Also:

newInstance(Class, Class[], Object[])

newInstanceByThread

public static final java.lang.Object newInstanceByThread(java.lang.String clsName)
                                                  throws java.lang.NoSuchMethodException,
                                                         java.lang.InstantiationException,
                                                         java.lang.reflect.InvocationTargetException,
                                                         java.lang.ClassNotFoundException,
                                                         java.lang.IllegalAccessException

Creates and initializes a new instance of the specified class name with default constructor, by use of forNameByThread(java.lang.String).

Throws:

java.lang.NoSuchMethodException

java.lang.InstantiationException

java.lang.reflect.InvocationTargetException

java.lang.ClassNotFoundException

java.lang.IllegalAccessException

forNameByThread

public static final java.lang.Class<?> forNameByThread(java.lang.String clsName)
                                                throws java.lang.ClassNotFoundException

Returns the Class object of the specified class name, using the current thread's context class loader.

It first tries Thread.currentThread().getContextClassLoader(), and then Classes's class loader if not found.

In additions, it handles the primitive types, such as int and double.

Parameters:

clsName - fully qualified name of the desired class

Returns:

the Class object representing the desired class

Throws:

java.lang.ClassNotFoundException - if the class cannot be located by the specified class loader

existsByThread

public static final boolean existsByThread(java.lang.String clsnm)

Returns whether the specified class exists for the current thread's context class loader.

Parameters:

clsnm - the class name to test

Since:

3.0.7

toInternalForm

public static final java.lang.String toInternalForm(java.lang.String clsName)

Change class name to internal form (e.g. byte[] -> [B). If already in internal form, then just return it.

getTopmostInterface

public static java.lang.Class<?> getTopmostInterface(java.lang.Class<?> cls,
                                                     java.lang.Class<?> subIF)

Gets the topmost interface of the specified class or interface that implements or extends the specified interface. For example, if A extends B, and C implements A, then getTopInterface(C, B) returns A.

The interfaces implemented by the specified class is checked first, and then the subclass.

Parameters:

cls - the class or interface

subIF - the sub-interface

Returns:

the topmost interface extending subIF, or null if subIF is not implemented by cls

getAllInterfaces

public static java.lang.Class<?>[] getAllInterfaces(java.lang.Class<?> cls)

Returns all interfaces that are implemented by the specified class.

Unlike Class.getInterfaces(), it recursively searches for all derived classes.

containsMethod

public static final boolean containsMethod(java.lang.Class<?> cls,
                                           java.lang.String name,
                                           java.lang.Class<?>[] paramTypes)

Tests whether a class contains the specified method. Only public methods are tested.

Parameters:

cls - the class to test

name - the method name

paramTypes - the list of parameter types

Returns:

true if it contains the method

correctFieldName

public static final java.lang.String correctFieldName(java.lang.String name)

Corrects a string to a valid Java name. Currently, it only removes '-' and capitalizes the succeeding character. Example, 'field-name' becomes 'fieldName'.

toMethodName

public static final java.lang.String toMethodName(java.lang.String attrName,
                                                  java.lang.String prefix)

Convert an attribute name, returned by toAttributeName, to a method name.

toMethodName("true", "is") => "isTrue"
toMethodName("true", "") => "true"

Parameters:

attrName - the attribute name

prefix - the prefix; one of is, get and set

Returns:

the method name

See Also:

toAttributeName(java.lang.String)

isAttribute

public static final boolean isAttribute(java.lang.String methodName)

Tests if a method name is an attribute, i.e., prefixing with is, get or set. Caller could then test if it is a setter or getter by charAt(0)=='s'.

Note 'set' is considered as an attribute, whose name is an empty string.

Parameters:

methodName - the method name to test

Returns:

true if it is setter or getter

toAttributeName

public static final java.lang.String toAttributeName(java.lang.String methodName)

Converts a method name to an attribute name by removing the prefix is, get or set, or null if it doesn't start with is, get or set.

The code is optimized for better performance.

Parameters:

methodName - the method name

Returns:

the attribute name; null if it is not an attribute name

See Also:

toMethodName(java.lang.String, java.lang.String)

parseMethod

public static final Classes.MethodInfo parseMethod(java.lang.String signature)
                                            throws IllegalSyntaxException

Gets the method information from a signature. It returns a method info with the return type, method name and two collections of arguments type and arguments name.

Parameters:

signature - the method signature.

Returns:

MethodInfo The method information including return type, method name and two collections for argument type and arguments name.

Throws:

IllegalSyntaxException

getMethodBySignature

public static final java.lang.reflect.Method getMethodBySignature(java.lang.Class<?> cls,
                                                                  java.lang.String signature,
                                                                  java.util.Collection<java.lang.String> params,
                                                                  ClassResolver resolver)
                                                           throws java.lang.NoSuchMethodException,
                                                                  java.lang.ClassNotFoundException

Gets the method based on the signature with a class resolver. It also returns the parameter names to the params list.

Like getMethodInPublic(Class, String, Class[]), it returns only public method in a public class/interface.

For example, "find(java.lang.String name)" will return the method with one String-typed argument and params will hold "name". The return type is optional (actually ignored).

If params is null, the parameter names are not returned and the signature could be simplified as "find(java.lang.String)".

A cache mechanism is implemented, so you don't need to cache it again in the caller.

Parameters:

cls - the class to look

signature - the method signature; the return type is optional.
Notice that the argument's type must be a full-qualified class name, unless its package is java.lang or it can be resolved by resolver.

params - the collection to hold the parameter names returned; null means no parameter names to return

resolver - the class resolver used to resolve the class specified in the signature. Ignored if null.

Throws:

java.lang.NoSuchMethodException

java.lang.ClassNotFoundException

Since:

6.0.0

getMethodBySignature

public static final java.lang.reflect.Method getMethodBySignature(java.lang.Class<?> cls,
                                                                  java.lang.String signature,
                                                                  java.util.Collection<java.lang.String> params)
                                                           throws java.lang.NoSuchMethodException,
                                                                  java.lang.ClassNotFoundException

Gets the method based on the signature. It also returns the parameter names to the params list.

Like getMethodInPublic(Class, String, Class[]), it returns only public method in a public class/interface.

For example, "find(java.lang.String name)" will return the method with one String-typed argument and params will hold "name". The return type is optional (actually ignored).

If params is null, the parameter names are not returned and the signature could be simplified as "find(java.lang.String)".

A cache mechanism is implemented, so you don't need to cache it again in the caller.

Parameters:

cls - the class to look

signature - the method signature; the return type is optional
Notice that the argument's type must be a full-qualified class name, unless its package is java.lang.

params - the collection to hold the parameter names returned; null means no parameter names to return

Throws:

java.lang.NoSuchMethodException

java.lang.ClassNotFoundException

getMethodInPublic

public static final java.lang.reflect.Method getMethodInPublic(java.lang.Class<?> cls,
                                                               java.lang.String name,
                                                               java.lang.Class<?>[] argTypes)
                                                        throws java.lang.NoSuchMethodException

Gets the method that is declared in a public class/interface.

Class.getMethod returns a public method but the class itself might not be public. However, in many cases, that class also implements a public interface or class.

This method will search all its public classes to look for the method that is 'real' public.

NoSuchMethodException is thrown if no public class/interface is found to have the method.

Throws:

java.lang.NoSuchMethodException

getMethodByObject

public static final java.lang.reflect.Method getMethodByObject(java.lang.Class<?> cls,
                                                               java.lang.String name,
                                                               java.lang.Object[] args)
                                                        throws java.lang.NoSuchMethodException

Gets one of the close method by specifying the arguments, rather than the argument types. It actually calls getCloseMethod(java.lang.Class, java.lang.String, java.lang.Class[]).

Throws:

java.lang.NoSuchMethodException

getCloseMethod

public static final java.lang.reflect.Method getCloseMethod(java.lang.Class<?> cls,
                                                            java.lang.String name,
                                                            java.lang.Class<?>[] argTypes)
                                                     throws java.lang.NoSuchMethodException

Gets one of the close methods -- a close method is a method with the same name and the compatible argument type. By compatible we mean the real method's argument type is the same as or a superclass of the specified one.

It might not be the best fit one, unless there is a method whose argument types are exactly argTypes.

You might specify the exact number in argTypes. If any of them is unknown, use null. Example, in the following, the first argument could be anything and the second is anything deriving from MyClass:
new Class[] {null, MyClass.class}

Note: if an argument accepts int, then Integer is considered as compatible (unlike Class.getMethod). So are long, byte...

A cache mechanism is implemented, so you don't need to cache it again in the caller.

Parameters:

cls - the class to locate the method

name - the method name

argTypes - an array of the argument classes; null to denote no argument at all (i.e., exact match). Any argTypes[i] could be null to denote any class.

Returns:

the method

Throws:

java.lang.NoSuchMethodException - if the method is not found

getCloseMethodBySubclass

public static final java.lang.reflect.Method getCloseMethodBySubclass(java.lang.Class<?> cls,
                                                                      java.lang.String name,
                                                                      java.lang.Class<?>[] argTypes)
                                                               throws java.lang.NoSuchMethodException

Like getCloseMethod(java.lang.Class, java.lang.String, java.lang.Class[]) to get a 'close' method, but it look for subclass of the argument (instead of superclass). In other words, it looks for the method whose argument type is the same as or a subclass of the specified one.

Throws:

java.lang.NoSuchMethodException

getCloseMethods

public static final java.lang.reflect.Method[] getCloseMethods(java.lang.Class<?> cls,
                                                               java.lang.String name,
                                                               java.lang.Class<?>[] argTypes)

Returns all close methods that match the specified condition, or a zero-length array if none is found.

Unlike getCloseMethod(java.lang.Class, java.lang.String, java.lang.Class[]), we don't cache the searched result, and it won't throw any exception.

getCloseMethodsBySubclass

public static final java.lang.reflect.Method[] getCloseMethodsBySubclass(java.lang.Class<?> cls,
                                                                         java.lang.String name,
                                                                         java.lang.Class<?>[] argTypes)

Like getCloseMethods(java.lang.Class, java.lang.String, java.lang.Class[]) to get all 'close' methods, but it look for subclass of the argument (instead of superclass). In other words, it looks for the method whose argument type is the same as or a subclass of the specified one.

getAccessibleObject

public static final java.lang.reflect.AccessibleObject getAccessibleObject(java.lang.Class<?> cls,
                                                                           java.lang.String name,
                                                                           java.lang.Class<?>[] argTypes,
                                                                           int flags)
                                                                    throws java.lang.NoSuchMethodException

Gets the specified accessible object, either a method or a field, by searching the specified name.

The search sequence is: (assume field name is body)>
getBody(...)
isBody(...)
body(...)
body

If B_SET is specified, setBody(...) is searched instead of getBody(...) and isBody(...). The field is searched only if argsType.length is 0 or 1.

Note: it uses getCloseMethod(java.lang.Class, java.lang.String, java.lang.Class[]) to get the method.

A cache mechanism is implemented, so you don't need to cache it again in the caller.

Parameters:

cls - the class to find

name - the name of the accessible object

argTypes - the parameter type of the method to find

flags - a combination of B_xxx or zero

Returns:

the accessible object; either Field or Method

Throws:

java.lang.NoSuchMethodException - if neither the set method of specified field nor the field itself not found

java.lang.SecurityException - if access to the information is denied

getAnyMethod

public static final java.lang.reflect.Method getAnyMethod(java.lang.Class<?> cls,
                                                          java.lang.String name,
                                                          java.lang.Class<?>[] argTypes)
                                                   throws java.lang.NoSuchMethodException

Gets the specified method by searching all methods including any access control and any base class. Note: you rarely need to call this method. In most cases, Class.getMethod, getCloseMethod(java.lang.Class, java.lang.String, java.lang.Class[]), and getMethodInPublic(java.lang.Class, java.lang.String, java.lang.Class[]) are what you need.

The search sequence is: this class's methods, and then the superclass's methods.

Note: public methods don't be treated different. If the caller wants to search public methods first, it has to call Class.getMethod first.

Parameters:

cls - the class to search

name - the method name

argTypes - the parameter array of types

Returns:

the Method object

Throws:

java.lang.NoSuchMethodException - if a matching method is not found.

java.lang.SecurityException - if access to the information is denied.

See Also:

getAccessibleObject(Class, String, Class[], int), getAnyField(Class, String)

getAnyField

public static final java.lang.reflect.Field getAnyField(java.lang.Class<?> cls,
                                                        java.lang.String name)
                                                 throws java.lang.NoSuchFieldException

Gets the specified field by searching all fields including any access control and any base class. The search sequence is: this class's fields, and then the superclass's fields.

Note: public fields don't be treated different. If the caller wants to search public fields first, it has to call Class.getField first.

Parameters:

cls - the class to search

name - the field name

Returns:

the Field object

Throws:

java.lang.NoSuchFieldException - if a matching field is not found.

java.lang.SecurityException - if access to the information is denied.

See Also:

getAccessibleObject(Class, String, Class[], int), getAnyMethod(Class, String, Class[])

getSuperClasses

public static final java.lang.Class<?>[] getSuperClasses(java.lang.Class<?> cls,
                                                         java.lang.Class<?>[] clsToCheck)

Searches thru each element of the specified array of classes, and returns classes that are super-classes (or equal) of the specified class.

Parameters:

cls - the specified class; null is not allowed

clsToCheck - the class array to check; null is acceptable

Returns:

a subset of clsToCheck that are super-class of cls; null if no one qualified

isPrimitiveWrapper

public static final boolean isPrimitiveWrapper(java.lang.Class<?> cls)

Check whether the specified class is a primitive or a primitive wrapper.

isNumeric

public static final boolean isNumeric(java.lang.Class<?> cls,
                                      boolean extend)

Checks whether the specified class is a numeric class.

Parameters:

extend - whether to consider Date, char, boolean, Character and Boolean as a numeric object.

coerce

public static java.lang.Object coerce(java.lang.Class<?> cls,
                                      java.lang.Object val)
                               throws java.lang.ClassCastException

Converts an object to the specified class. It is the same as coerce(cls, val, true).

Parameters:

val - the value.

Throws:

java.lang.ClassCastException - if failed to convert

See Also:

coerce(Class, Object, boolean)

coerce

public static java.lang.Object coerce(java.lang.Class<?> cls,
                                      java.lang.Object val,
                                      boolean nullable)
                               throws java.lang.ClassCastException

Converts to the specified type.

Parameters:

nullable - whether the result could be null. If false, 0 is used for number, the default constructor is used for others. coerce(Class, Object) is a special case that is equivalent to nullable=true.

Throws:

java.lang.ClassCastException - if failed to convert