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== Although the type of o2 is an interface, getSuperclass() returns the object"s superclass ==



<source lang="java">
public class Main {
public static void main(String[] argv) throws Exception {
Runnable o2 = new Runnable() {
public void run() {
}
};
Class sup = o2.getClass().getSuperclass(); // java.lang.Object
}
}</source>



== Checking whether String is an interface or class ==



<source lang="java">
public class Main {
public static void main(String[] argv) throws Exception {
Class clazz = String.class;
boolean isInterface = clazz.isInterface();
System.out.println("Is Interface = " + isInterface);
}
}</source>



== Get all interface and object classes that are generalizations of the provided class ==



<source lang="java">
/*
* The contents of this file are subject to the Sapient Public License
* Version 1.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
* http://carbon.sf.net/License.html.
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for
* the specific language governing rights and limitations under the License.
*
* The Original Code is The Carbon Component Framework.
*
* The Initial Developer of the Original Code is Sapient Corporation
*
* Copyright (C) 2003 Sapient Corporation. All Rights Reserved.
*/

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
/**
*
*
* Copyright 2003 Sapient
* @since carbon 2.0
* @author Greg Hinkle, March 2003
* @version $Revision: 1.5 $($Author: dvoet $ / $Date: 2003/05/05 21:21:23 $)
*/
public class ClassUtil {
/**
* Retrieves all interfaces implemented by a specified interface
* including all recursively extended interfaces and the classes supplied
* int the parameter.
* @param childInterfaces a set of interfaces
* @return Class[] an array of interfaces that includes those specifed
* in childInterfaces plus all of those interfaces" super interfaces
*/
public static Class[] getSuperInterfaces(Class[] childInterfaces) {
List allInterfaces = new ArrayList();
for (int i = 0; i < childInterfaces.length; i++) {
allInterfaces.add(childInterfaces[i]);
allInterfaces.addAll(
Arrays.asList(
getSuperInterfaces(childInterfaces[i].getInterfaces())));
}
return (Class[]) allInterfaces.toArray(new Class[allInterfaces.size()]);
}
/**
* Builds an <b>unordered</b> set of all interface and object classes that
* are generalizations of the provided class.
* @param classObject the class to find generalization of.
* @return a Set of class objects.
*/
public static Set getGeneralizations(Class classObject) {
Set generalizations = new HashSet();
generalizations.add(classObject);
Class superClass = classObject.getSuperclass();
if (superClass != null) {
generalizations.addAll(getGeneralizations(superClass));
}
Class[] superInterfaces = classObject.getInterfaces();
for (int i = 0; i < superInterfaces.length; i++) {
Class superInterface = superInterfaces[i];
generalizations.addAll(getGeneralizations(superInterface));
}
return generalizations;
}
}</source>



== Get Super Interfaces ==



<source lang="java">
/*
* The contents of this file are subject to the Sapient Public License
* Version 1.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
* http://carbon.sf.net/License.html.
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for
* the specific language governing rights and limitations under the License.
*
* The Original Code is The Carbon Component Framework.
*
* The Initial Developer of the Original Code is Sapient Corporation
*
* Copyright (C) 2003 Sapient Corporation. All Rights Reserved.
*/

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
/**
*
*
* Copyright 2003 Sapient
* @since carbon 2.0
* @author Greg Hinkle, March 2003
* @version $Revision: 1.5 $($Author: dvoet $ / $Date: 2003/05/05 21:21:23 $)
*/
public class ClassUtil {
/**
* Retrieves all interfaces implemented by a specified interface
* including all recursively extended interfaces and the classes supplied
* int the parameter.
* @param childInterfaces a set of interfaces
* @return Class[] an array of interfaces that includes those specifed
* in childInterfaces plus all of those interfaces" super interfaces
*/
public static Class[] getSuperInterfaces(Class[] childInterfaces) {
List allInterfaces = new ArrayList();
for (int i = 0; i < childInterfaces.length; i++) {
allInterfaces.add(childInterfaces[i]);
allInterfaces.addAll(
Arrays.asList(
getSuperInterfaces(childInterfaces[i].getInterfaces())));
}
return (Class[]) allInterfaces.toArray(new Class[allInterfaces.size()]);
}
/**
* Builds an <b>unordered</b> set of all interface and object classes that
* are generalizations of the provided class.
* @param classObject the class to find generalization of.
* @return a Set of class objects.
*/
public static Set getGeneralizations(Class classObject) {
Set generalizations = new HashSet();
generalizations.add(classObject);
Class superClass = classObject.getSuperclass();
if (superClass != null) {
generalizations.addAll(getGeneralizations(superClass));
}
Class[] superInterfaces = classObject.getInterfaces();
for (int i = 0; i < superInterfaces.length; i++) {
Class superInterface = superInterfaces[i];
generalizations.addAll(getGeneralizations(superInterface));
}
return generalizations;
}
}</source>



== If a class object is an interface or a class ==



<source lang="java">
public class Main {
public static void main(String[] args) {
// Checking whether Cloneable is an interface or class
Class clazz = Cloneable.class;
boolean isInterface = clazz.isInterface();
System.out.println("Is Interface = " + isInterface);
}
}</source>



== Listing the Interfaces That a Class Implements ==



<source lang="java">
public class Main {
public static void main(String[] argv) throws Exception {
Class cls = java.lang.String.class;
Class[] intfs = cls.getInterfaces();
}
}</source>



== Listing the Interfaces That an Interface Extends ==



<source lang="java">
public class Main {
public static void main(String[] argv) throws Exception {
Class cls = java.util.List.class;
Class[] intfs = cls.getInterfaces(); // java.util.Collection
}
}</source>



== Return Returns true if type is implementing Map ==



<source lang="java">
// $Id: ReflectionHelper.java 16271 2009-04-07 20:20:12Z hardy.ferentschik $
/*
* JBoss, Home of Professional Open Source
* Copyright 2008, Red Hat Middleware LLC, and individual contributors
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* http://www.apache.org/licenses/LICENSE-2.0
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.beans.Introspector;
import java.lang.annotation.Annotation;
import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Member;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.WildcardType;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
/**
* Some reflection utility methods.
*
* @author Hardy Ferentschik
*/
public class ReflectionHelper {
/**
* @param type the type to check.
*
* @return Returns <code>true</code> if <code>type</code> is implementing <code>Map</code>, <code>false</code> otherwise.
*/
public static boolean isMap(Type type) {
if ( type instanceof Class && isMapClass( ( Class ) type ) ) {
return true;
}
if ( type instanceof ParameterizedType ) {
return isMap( ( ( ParameterizedType ) type ).getRawType() );
}
if ( type instanceof WildcardType ) {
Type[] upperBounds = ( ( WildcardType ) type ).getUpperBounds();
return upperBounds.length != 0 && isMap( upperBounds[0] );
}
return false;
}
/**
* Checks whether the specified class parameter is an instance of a collection class.
*
* @param clazz <code>Class</code> to check.
*
* @return <code>true</code> is <code>clazz</code> is instance of a collection class, <code>false</code> otherwise.
*/
private static boolean isMapClass(Class<?> clazz) {
List<Class<?>> classes = new ArrayList<Class<?>>();
computeClassHierarchy( clazz, classes );
return classes.contains( Map.class );
}
/**
* Get all superclasses and interfaces recursively.
*
* @param clazz The class to start the search with.
* @param classes List of classes to which to add all found super classes and interfaces.
*/
private static void computeClassHierarchy(Class<?> clazz, List<Class<?>> classes) {
for ( Class current = clazz; current != null; current = current.getSuperclass() ) {
if ( classes.contains( current ) ) {
return;
}
classes.add( current );
for ( Class currentInterface : current.getInterfaces() ) {
computeClassHierarchy( currentInterface, classes );
}
}
}
}</source>



== Returns true if a class implements Serializable and false otherwise. ==



<source lang="java">
import java.io.Serializable;
/*
* JCommon : a free general purpose class library for the Java(tm) platform
*
*
* (C) Copyright 2000-2005, by Object Refinery Limited and Contributors.
*
* Project Info: http://www.jfree.org/jcommon/index.html
*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*
* This library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
* USA.
*
* [Java is a trademark or registered trademark of Sun Microsystems, Inc.
* in the United States and other countries.]
*
* ------------
* IOUtils.java
* ------------
* (C)opyright 2002-2004, by Thomas Morgner and Contributors.
*
* Original Author: Thomas Morgner;
* Contributor(s): David Gilbert (for Object Refinery Limited);
*
* $Id: IOUtils.java,v 1.8 2009/01/22 08:34:58 taqua Exp $
*
* Changes
* -------
* 26-Jan-2003 : Initial version
* 23-Feb-2003 : Documentation
* 25-Feb-2003 : Fixed Checkstyle issues (DG);
* 29-Apr-2003 : Moved to jcommon
* 04-Jan-2004 : Fixed JDK 1.2.2 issues with createRelativeURL;
* added support for query strings within these urls (TM);
*/

public class Main {
/**
* Returns <code>true</code> if a class implements <code>Serializable</code>
* and <code>false</code> otherwise.
*
* @param c the class.
*
* @return A boolean.
*/
public static boolean isSerializable(final Class c) {
/**
final Class[] interfaces = c.getInterfaces();
for (int i = 0; i < interfaces.length; i++) {
if (interfaces[i].equals(Serializable.class)) {
return true;
}
}
Class cc = c.getSuperclass();
if (cc != null) {
return isSerializable(cc);
}
*/
return (Serializable.class.isAssignableFrom(c));
}
}</source>



== The interfaces for a primitive type is an empty array ==



<source lang="java">
public class Main {
public static void main(String[] argv) throws Exception {
Class cls = int.class;
Class[] intfs = cls.getInterfaces(); // []
}
}</source>



== The superclass of interfaces is always null ==



<source lang="java">
public class Main {
public static void main(String[] argv) throws Exception {
Class cls = java.lang.Cloneable.class;
Class sup = cls.getSuperclass(); // null
}
}</source>

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Java Tutorial/Reflection/Interface - История изменений

в 17:44, 31 мая 2010

Admin: 1 версия