Commons Attributes example source code file (AttributeUtil.java)

This example Commons Attributes source code file (AttributeUtil.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons Attributes tags/keywords

arraylist, arraylist, attributeutil, class, class, collection, collection, iterator, nullpointerexception, nullpointerexception, object, reflection, util

The Commons Attributes AttributeUtil.java source code

/*
 * Copyright 2003-2004 The Apache Software Foundation
 * 
 * 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.
 */
package org.apache.commons.attributes;

import java.lang.reflect.Field;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.Collection;
import java.util.Collections;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.WeakHashMap;

/**
 * Commonly used convenience functions.
 *
 * @since 2.1
 */
public class AttributeUtil {
    
    /**
     * Filters a Collection of <code>Class objects. The returned collection
     * only contains those classes that have an attribute of the specified type.
     * That is, for each Class clazz in the 
     * returned collection, 
     * <code>clazz != null && Attributes.hasAttributeType (clazz, attributeClass) 
     * is true.
     * 
     * @param classes Collection of Classes to filter. May contain <code>null references,
     *                but may not itself be <code>null.
     * @param attributeClass the class to filter based on.
     *
     * @since 2.1
     */
    public static Collection getClassesWithAttributeType (Collection classes, Class attributeClass) {
        if (classes == null) {
            throw new NullPointerException ("classes");
        }
        
        if (attributeClass == null) {
            throw new NullPointerException ("attributeClass");
        }
        
        ArrayList result = new ArrayList ();
        Iterator iter = classes.iterator ();
        while (iter.hasNext ()) {
            Class clazz = (Class) iter.next ();
            if (clazz != null) {
                if (Attributes.hasAttributeType (clazz, attributeClass)) {
                    result.add (clazz);
                }
            }
        }
        
        return result;
    }
    
    /**
     * Filters a collection of objects. The returned collection
     * only contains those objects whose class have an attribute 
     * of the specified type. That is, for each Object o in the 
     * returned collection, 
     * <code>o != null && Attributes.hasAttributeType (o.getClass (), attributeClass) 
     * is true.
     *
     * @param objects Collection of objects to filter. May contain <code>null references,
     *                but may not itself be <code>null.
     * @param attributeClass the class to filter based on.
     *
     * @since 2.1
     */
    public static Collection getObjectsWithAttributeType (Collection objects, Class attributeClass) {
        if (objects == null) {
            throw new NullPointerException ("objects");
        }
        
        if (attributeClass == null) {
            throw new NullPointerException ("attributeClass");
        }
        
        ArrayList result = new ArrayList ();
        Iterator iter = objects.iterator ();
        while (iter.hasNext ()) {
            Object object = iter.next ();
            if (object != null) {
                Class clazz = object.getClass ();
                if (Attributes.hasAttributeType (clazz, attributeClass)) {
                    result.add (object);
                }
            }
        }
        
        return result;        
    }
}