classutils.java

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/* ====================================================================
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 *    notice, this list of conditions and the following disclaimer.
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 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgement may appear in the software itself,
 *    if and wherever such third-party acknowledgements normally appear.
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package org.apache.commons.lang;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
/**
 * <p>Operates on classes without using reflection.</p>
 *
 * <p>This class handles invalid <code>null</code> inputs as best it can.
 * Each method documents its behaviour in more detail.</p>
 *
 * @author Stephen Colebourne
 * @author Gary Gregory
 * @since 2.0
 * @version $Id: ClassUtils.java,v 1.21 2003/08/22 17:25:33 ggregory Exp $
 */
public class ClassUtils {

    /**
     * <p>The package separator character: <code>&#x2e;</code>.</p>
     */
    public static final char PACKAGE_SEPARATOR_CHAR = '.';
    
    /**
     * <p>The package separator String: <code>&#x2e;</code>.</p>
     */
    public static final String PACKAGE_SEPARATOR = String.valueOf(PACKAGE_SEPARATOR_CHAR);
    
    /**
     * <p>The inner class separator character: <code>$</code>.</p>
     */
    public static final char INNER_CLASS_SEPARATOR_CHAR = '$';
    
    /**
     * <p>The inner class separator String: <code>$</code>.</p>
     */
    public static final String INNER_CLASS_SEPARATOR = String.valueOf(INNER_CLASS_SEPARATOR_CHAR);
    
    /**
     * <p>ClassUtils instances should NOT be constructed in standard programming.
     * Instead, the class should be used as
     * <code>ClassUtils.getShortClassName(cls)</code>.</p>
     *
     * <p>This constructor is public to permit tools that require a JavaBean
     * instance to operate.</p>
     */
    public ClassUtils() {
    }

    // Short class name
    // ----------------------------------------------------------------------
    /**
     * <p>Gets the class name minus the package name for an <code>Object</code>.</p>
     * 
     * @param object  the class to get the short name for, may be null
     * @param valueIfNull  the value to return if null
     * @return the class name of the object without the package name, or the null value
     */
    public static String getShortClassName(Object object, String valueIfNull) {
        if (object == null) {
            return valueIfNull;
        }
        return getShortClassName(object.getClass().getName());
    }
    
    /**
     * <p>Gets the class name minus the package name from a <code>Class</code>.</p>
     * 
     * @param cls  the class to get the short name for, must not be
     *  <code>null</code>
     * @return the class name without the package name
     * @throws IllegalArgumentException if the class is <code>null</code>
     */
    public static String getShortClassName(Class cls) {
        if (cls == null) {
            throw new IllegalArgumentException("The class must not be null");
        }
        return getShortClassName(cls.getName());
    }
    
    /**
     * <p>Gets the class name minus the package name from a String.</p>
     *
     * <p>The string passed in is assumed to be a class name - it is not checked.</p>
     * 
     * @param className  the className to get the short name for,
     *  must not be empty or <code>null</code>
     * @return the class name of the class without the package name
     * @throws IllegalArgumentException if the className is empty
     */
    public static String getShortClassName(String className) {
        if (StringUtils.isEmpty(className)) {
            throw new IllegalArgumentException("The class name must not be empty");
        }
        char[] chars = className.toCharArray();
        int lastDot = 0;
        for (int i = 0; i < chars.length; i++) {
            if (chars[i] == PACKAGE_SEPARATOR_CHAR) {
                lastDot = i + 1;
            } else if (chars[i] == INNER_CLASS_SEPARATOR_CHAR) {  // handle inner classes
                chars[i] = PACKAGE_SEPARATOR_CHAR;
            }
        }
        return new String(chars, lastDot, chars.length - lastDot);
    }
    
    // Package name
    // ----------------------------------------------------------------------
    /**
     * <p>Gets the package name of an <code>Object</code>.</p>
     * 
     * @param object  the class to get the package name for, may be null
     * @param valueIfNull  the value to return if null
     * @return the package name of the object, or the null value
     */
    public static String getPackageName(Object object, String valueIfNull) {
        if (object == null) {
            return valueIfNull;
        }
        return getPackageName(object.getClass().getName());
    }
    
    /**
     * <p>Gets the package name of a <code>Class</code>.</p>
     * 
     * @param cls  the class to get the package name for,
     *  must not be <code>null</code>
     * @return the package name
     * @throws IllegalArgumentException if the class is <code>null</code>
     */
    public static String getPackageName(Class cls) {
        if (cls == null) {
            throw new IllegalArgumentException("The class must not be null");
        }
        return getPackageName(cls.getName());
    }
    
    /**
     * <p>Gets the package name from a <code>String</code>.</p>
     *
     * <p>The string passed in is assumed to be a class name - it is not checked.</p>
     * 
     * @param className  the className to get the package name for,
     *  must not be empty or <code>null</code>
     * @return the package name
     * @throws IllegalArgumentException if the className is empty
     */
    public static String getPackageName(String className) {
        if (StringUtils.isEmpty(className)) {
            throw new IllegalArgumentException("The class name must not be empty");
        }
        int i = className.lastIndexOf(PACKAGE_SEPARATOR_CHAR);
        if (i == -1) {
            return "";
        }
        return className.substring(0, i);
    }
    
    // Superclasses/Superinterfaces
    // ----------------------------------------------------------------------
    /**
     * <p>Gets a <code>List</code> of superclasses for the given class.</p>
     * 
     * @param cls  the class to look up, must not be <code>null</code>
     * @return the <code>List</code> of superclasses in order going up from this one
     *  <code>null</code> if null input
     */
    public static List getAllSuperclasses(Class cls) {
        if (cls == null) {
            return null;
        }
        List classes = new ArrayList();
        Class superclass = cls.getSuperclass();
        while (superclass != null) {
            classes.add(superclass);
            superclass = superclass.getSuperclass();
        }
        return classes;
    }
    
    /**
     * <p>Gets a <code>List</code> of all interfaces implemented by the given
     * class and its superclasses.</p>
     *
     * <p>The order is determined by looking through each interface in turn as
     * declared in the source file and following its hieracrchy up. Then each 
     * superclass is considered in the same way. Later duplicates are ignored, 
     * so the order is maintained.</p>
     * 
     * @param cls  the class to look up, must not be <code>null</code>
     * @return the <code>List</code> of interfaces in order,
     *  <code>null</code> if null input
     */
    public static List getAllInterfaces(Class cls) {
        if (cls == null) {
            return null;
        }
        List list = new ArrayList();
        while (cls != null) {
            Class[] interfaces = cls.getInterfaces();
            for (int i = 0; i < interfaces.length; i++) {
                if (list.contains(interfaces[i]) == false) {
                    list.add(interfaces[i]);
                }
                List superInterfaces = getAllInterfaces(interfaces[i]);
                for (Iterator it = superInterfaces.iterator(); it.hasNext();) {
                    Class intface = (Class) it.next();
                    if (list.contains(intface) == false) {
                        list.add(intface);
                    }
                }
            }
            cls = cls.getSuperclass();
        }