classutils.java

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        return list;
    }
    
//    /**
//     * <p>Gets a <code>List</code> of subclasses of the specified class.</p>
//     *
//     * <p>This method searches the classpath to find all the subclasses
//     * of a particular class available. No classes are loaded, the 
//     * returned list contains class names, not classes.</p>
//     *
//     * @param cls  the class to find subclasses for
//     * @return the <code>List</code> of subclass String class names
//     * @throws IllegalArgumentException if the class is <code>null</code>
//     */
//    public static List getAllSubclassNames(Class cls) {
//        if (cls == null) {
//            throw new IllegalArgumentException("The class must not be null");
//        }
//        // TODO Use JavaWorld tip for searching the classpath
//        return null;
//    }

//    /**
//     * <p>Gets a <code>List</code> of subclasses of the specified class.</p>
//     *
//     * <p>This method searches the classpath to find all the subclasses
//     * of a particular class available.</p>
//     *
//     * @param cls  the class to find subclasses for
//     * @return the <code>List</code> of subclasses
//     * @throws IllegalArgumentException if the class is <code>null</code>
//     */
//    public static List getAllSubclasses(Class cls) {
//        List names = getAllSubclassNames(cls);
//        return convertClassNamesToClasses(names);
//    }

//    /**
//     * <p>Gets a <code>List</code> of implementations of the specified interface.</p>
//     *
//     * <p>This method searches the classpath to find all the implementations
//     * of a particular interface available. No classes are loaded, the 
//     * returned list contains class names, not classes.</p>
//     *
//     * @param cls  the class to find sub classes for
//     * @return the <code>List</code> of implementation String class names
//     * @throws IllegalArgumentException if the class is <code>null</code>
//     */
//    public static List getAllImplementationClassNames(Class cls) {
//        if (cls == null) {
//            throw new IllegalArgumentException("The class must not be null");
//        }
//        // TODO Use JavaWorld tip for searching the classpath
//        return null;
//    }

    // Convert list
    // ----------------------------------------------------------------------
    /**
     * <p>Given a <code>List</code> of class names, this method converts them into classes.</p>
     *
     * <p>A new <code>List</code> is returned. If the class name cannot be found, <code>null</code>
     * is stored in the <code>List</code>. If the class name in the <code>List</code> is
     * <code>null</code>, <code>null</code> is stored in the output <code>List</code>.</p>
     * 
     * @param classNames  the classNames to change
     * @return a <code>List</code> of Class objects corresponding to the class names,
     *  <code>null</code> if null input
     * @throws ClassCastException if classNames contains a non String entry
     */
    public static List convertClassNamesToClasses(List classNames) {
        if (classNames == null) {
            return null;
        }
        List classes = new ArrayList(classNames.size());
        for (Iterator it = classNames.iterator(); it.hasNext();) {
            String className = (String) it.next();
            try {
                classes.add(Class.forName(className));
            } catch (Exception ex) {
                classes.add(null);
            }
        }
        return classes;
    }
    
    /**
     * <p>Given a <code>List</code> of <code>Class</code> objects, this method converts
     * them into class names.</p>
     *
     * <p>A new <code>List</code> is returned. <code>null</code> objects will be copied into
     * the returned list as <code>null</code>.</p>
     * 
     * @param classes  the classes to change
     * @return a <code>List</code> of Class objects corresponding to the class names,
     *  <code>null</code> if null input
     * @throws ClassCastException if classNames contains a non Class or null entry
     */
    public static List convertClassesToClassNames(List classes) {
        if (classes == null) {
            return null;
        }
        List classNames = new ArrayList(classes.size());
        for (Iterator it = classes.iterator(); it.hasNext();) {
            Class cls = (Class) it.next();
            if (cls == null) {
                classNames.add(null);
            } else {
                classNames.add(cls.getName());
            }
        }
        return classNames;
    }
    
    // Is assignable
    // ----------------------------------------------------------------------
    /**
     * <p>Checks if an array of Classes can be assigned to another array of Classes.</p>
     *
     * <p>This method calls {@link #isAssignable(Class, Class) 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 compatable with a set of method parameter types
     * (the second parameter).</p>
     *
     * <p>Unlike the {@link Class#isAssignableFrom(java.lang.Class)} method, this
     * method takes into account widenings of primitive classes and
     * <code>null</code>s.</p>
     *
     * <p>Primitive widenings allow an int to be assigned to a <code>long</code>,
     * <code>float</code> or <code>double</code>. This method returns the correct
     * result for these cases.</p>
     *
     * <p><code>Null</code> may be assigned to any reference type. This method will
     * return <code>true</code> if <code>null</code> is passed in and the toClass is
     * non-primitive.</p>
     *
     * <p>Specifically, this method tests whether the type represented by the
     * specified <code>Class</code> parameter can be converted to the type
     * represented by this <code>Class</code> object via an identity conversion
     * widening primitive or widening reference conversion. See 
     * <em><a href="http://java.sun.com/docs/books/jls/">The Java Language Specification</a></em>,
     * sections 5.1.1, 5.1.2 and 5.1.4 for details.</p>
     *
     * @param classArray  the array of Classes to check, may be <code>null</code>
     * @param toClassArray  the array of Classes to try to assign into, may be <code>null</code>
     * @return <code>true</code> if assignment possible
     */
    public static boolean isAssignable(Class[] classArray, Class[] toClassArray) {
        if (ArrayUtils.isSameLength(classArray, toClassArray) == false) {
            return false;
        }
        if (classArray == null) {
            classArray = ArrayUtils.EMPTY_CLASS_ARRAY;
        }
        if (toClassArray == null) {
            toClassArray = ArrayUtils.EMPTY_CLASS_ARRAY;
        }
        for (int i = 0; i < classArray.length; i++) {
            if (isAssignable(classArray[i], toClassArray[i]) == false) {
                return false;
            }
        }
        return true;
    }
    
    /**
     * <p>Checks if one <code>Class</code> can be assigned to a variable of
     * another <code>Class</code>.</p>
     *
     * <p>Unlike the {@link Class#isAssignableFrom(java.lang.Class)} method,
     * this method takes into account widenings of primitive classes and
     * <code>null</code>s.</p>
     *
     * <p>Primitive widenings allow an int to be assigned to a long, float or
     * double. This method returns the correct result for these cases.</p>
     *
     * <p><code>Null</code> may be assigned to any reference type. This method
     * will return <code>true</code> if <code>null</code> is passed in and the
     * toClass is non-primitive.</p>
     *
     * <p>Specifically, this method tests whether the type represented by the
     * specified <code>Class</code> parameter can be converted to the type
     * represented by this <code>Class</code> object via an identity conversion
     * widening primitive or widening reference conversion. See 
     * <em><a href="http://java.sun.com/docs/books/jls/">The Java Language Specification</a></em>,
     * sections 5.1.1, 5.1.2 and 5.1.4 for details.</p>
     *
     * @param cls  the Class to check, may be null
     * @param toClass  the Class to try to assign into, returns false if null
     * @return <code>true</code> if assignment possible
     */
    public static boolean isAssignable(Class cls, Class toClass) {
        if (toClass == null) {
            return false;
        }
        // have to check for null, as isAssignableFrom doesn't
        if (cls == null) {
            return !(toClass.isPrimitive());
        }
        if (cls.equals(toClass)) {
            return true;
        }
        if (cls.isPrimitive()) {
            if (toClass.isPrimitive() == false) {
                return false;
            }
            if (Integer.TYPE.equals(cls)) {
                return Long.TYPE.equals(toClass) 
                    || Float.TYPE.equals(toClass) 
                    || Double.TYPE.equals(toClass);
            }
            if (Long.TYPE.equals(cls)) {
                return Float.TYPE.equals(toClass) 
                    || Double.TYPE.equals(toClass);
            }
            if (Boolean.TYPE.equals(cls)) {
                return false;
            }
            if (Double.TYPE.equals(cls)) {
                return false;
            }
            if (Float.TYPE.equals(cls)) {
                return Double.TYPE.equals(toClass);
            }
            if (Character.TYPE.equals(cls)) {
                return Integer.TYPE.equals(toClass) 
                    || Long.TYPE.equals(toClass) 
                    || Float.TYPE.equals(toClass) 
                    || Double.TYPE.equals(toClass);
            }
            if (Short.TYPE.equals(cls)) {
                return Integer.TYPE.equals(toClass) 
                    || Long.TYPE.equals(toClass) 
                    || Float.TYPE.equals(toClass) 
                    || Double.TYPE.equals(toClass);
            }
            if (Byte.TYPE.equals(cls)) {
                return Short.TYPE.equals(toClass) 
                    || Integer.TYPE.equals(toClass) 
                    || Long.TYPE.equals(toClass) 
                    || Float.TYPE.equals(toClass) 
                    || Double.TYPE.equals(toClass);
            }
            // should never get here
            return false;
        }
        return toClass.isAssignableFrom(cls);
    }
    
    // Inner class
    // ----------------------------------------------------------------------
    /**
     * <p>Is the specified class an inner class or static nested class.</p>
     * 
     * @param cls  the class to check
     * @return <code>true</code> if the class is an inner or static nested class,
     *  false if not or <code>null</code>
     */
    public static boolean isInnerClass(Class cls) {
        if (cls == null) {
            return false;
        }
        return (cls.getName().indexOf(INNER_CLASS_SEPARATOR_CHAR) >= 0);
    }
    
}