Append, filter and get the size of collections : Collection « Collections Data Structure « Java

Java
1. 2D Graphics GUI
2. 3D
3. Advanced Graphics
4. Ant
5. Apache Common
6. Chart
7. Class
8. Collections Data Structure
9. Data Type
10. Database SQL JDBC
11. Design Pattern
12. Development Class
13. EJB3
14. Email
15. Event
16. File Input Output
17. Game
18. Generics
19. GWT
20. Hibernate
21. I18N
22. J2EE
23. J2ME
24. JDK 6
25. JNDI LDAP
26. JPA
27. JSP
28. JSTL
29. Language Basics
30. Network Protocol
31. PDF RTF
32. Reflection
33. Regular Expressions
34. Scripting
35. Security
36. Servlets
37. Spring
38. Swing Components
39. Swing JFC
40. SWT JFace Eclipse
41. Threads
42. Tiny Application
43. Velocity
44. Web Services SOA
45. XML
Java Tutorial
Java Source Code / Java Documentation
Java Open Source
Jar File Download
Java Articles
Java Products
Java by API
Photoshop Tutorials
Maya Tutorials
Flash Tutorials
3ds-Max Tutorials
Illustrator Tutorials
GIMP Tutorials
C# / C Sharp
C# / CSharp Tutorial
C# / CSharp Open Source
ASP.Net
ASP.NET Tutorial
JavaScript DHTML
JavaScript Tutorial
JavaScript Reference
HTML / CSS
HTML CSS Reference
C / ANSI-C
C Tutorial
C++
C++ Tutorial
Ruby
PHP
Python
Python Tutorial
Python Open Source
SQL Server / T-SQL
SQL Server / T-SQL Tutorial
Oracle PL / SQL
Oracle PL/SQL Tutorial
PostgreSQL
SQL / MySQL
MySQL Tutorial
VB.Net
VB.Net Tutorial
Flash / Flex / ActionScript
VBA / Excel / Access / Word
XML
XML Tutorial
Microsoft Office PowerPoint 2007 Tutorial
Microsoft Office Excel 2007 Tutorial
Microsoft Office Word 2007 Tutorial
Java » Collections Data Structure » CollectionScreenshots 
Append, filter and get the size of collections
  
/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.w3c.dom.NodeList;

/**
 * A number of helper methods for working with collections
 *
 @version $Revision: 747062 $
 */
public final class CollectionHelper {

    /**
     * Utility classes should not have a public constructor.
     */
    private CollectionHelper() {
    }

    /**
     * Returns the size of the collection if it can be determined to be a collection
     *
     @param value the collection
     @return the size, or <tt>null</tt> if not a collection
     */
    public static Integer size(Object value) {
        if (value != null) {
            if (value instanceof Collection) {
                Collection collection = (Collection)value;
                return collection.size();
            else if (value instanceof Map) {
                Map map = (Map)value;
                return map.size();
            else if (value instanceof Object[]) {
                Object[] array = (Object[])value;
                return array.length;
            else if (value.getClass().isArray()) {
                return Array.getLength(value);
            else if (value instanceof NodeList) {
                NodeList nodeList = (NodeList)value;
                return nodeList.getLength();
            }
        }
        return null;
    }

    /**
     * Sets the value of the entry in the map for the given key, though if the
     * map already contains a value for the given key then the value is appended
     * to a list of values.
     *
     @param map the map to add the entry to
     @param key the key in the map
     @param value the value to put in the map
     */
    @SuppressWarnings("unchecked")
    public static void appendValue(Map map, Object key, Object value) {
        Object oldValue = map.get(key);
        if (oldValue != null) {
            List list;
            if (oldValue instanceof List) {
                list = (List)oldValue;
            else {
                list = new ArrayList();
                list.add(oldValue);
            }
            list.add(value);
        else {
            map.put(key, value);
        }
    }

    /**
     * Filters the given list to skip instanceof filter objects.
     
     @param list  the list
     @param filters  objects to skip
     @return a new list without the filtered objects
     */
    @SuppressWarnings("unchecked")
    public static List filterList(List list, Object... filters) {
        List answer = new ArrayList();
        for (Object o : list) {
            for (Object filter : filters) {
                if (!o.getClass().isInstance(filter)) {
                    answer.add(o);
                }
            }
        }
        return answer;
    }

    public static String collectionAsCommaDelimitedString(String[] col) {
        if (col == null || col.length == 0) {
            return "";
        }
        return collectionAsCommaDelimitedString(Arrays.asList(col));
    }

    public static String collectionAsCommaDelimitedString(Collection col) {
        if (col == null || col.isEmpty()) {
            return "";
        }

        StringBuilder sb = new StringBuilder();
        Iterator it = col.iterator();
        while (it.hasNext()) {
            sb.append(it.next());
            if (it.hasNext()) {
                sb.append(",");
            }
        }

        return sb.toString();
    }
    
}

   
    
  
Related examples in the same category
1. Disjoint two collections
2. Whether Collection only contains a single unique object
3. Simple implementation of a generic Bag
4. Find a value of the given type in the given Collection
5. Check whether the given Collection contains the given element instance.
6. Return the first element in 'candidates' that is contained in source
7. Return true if any element in 'candidates' is contained in source
8. A utility class for working with attribute and parameter collections used by Spring Web FLow
9. Is collection is empty, and all of its elements are empty
10. Deep clone collection: Returns a new collection containing clones of all the items in the specified collection.
11. Get the difference of two collections
12. The collection related utilities
13. A combination of two collections into a collection
14. Clone an array
15. Clones a map and prefixes the keys in the clone
16. Clones the lhs map and add all things from the rhs map.
www.java2java.com | Contact Us
Copyright 2009 - 12 Demo Source and Support. All rights reserved.
All other trademarks are property of their respective owners.