Java/Collections Data Structure/Paging

Implementation of PaginatedList backed by an ArrayList

 
/*
 *  Copyright 2004 Clinton Begin
 *
 *  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.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
/**
 * Implementation of PaginatedList backed by an ArrayList
 * 
 */
public class PaginatedArrayList implements PaginatedList {
  private static final ArrayList EMPTY_LIST = new ArrayList(0);
  private List list;
  private List page;
  private int pageSize;
  private int index;
  /**
   * @param pageSize
   */
  public PaginatedArrayList(int pageSize) {
    this.pageSize = pageSize;
    this.index = 0;
    this.list = new ArrayList();
    repaginate();
  }
  /**
   * Constructor to set the initial size and the page size
   * 
   * @param initialCapacity -
   *          the initial size
   * @param pageSize -
   *          the page size
   */
  public PaginatedArrayList(int initialCapacity, int pageSize) {
    this.pageSize = pageSize;
    this.index = 0;
    this.list = new ArrayList(initialCapacity);
    repaginate();
  }
  /**
   * Constructor to create an instance using an existing collection
   * 
   * @param c -
   *          the collection to build the instance with
   * @param pageSize -
   *          the page size
   */
  public PaginatedArrayList(Collection c, int pageSize) {
    this.pageSize = pageSize;
    this.index = 0;
    this.list = new ArrayList(c);
    repaginate();
  }
  private void repaginate() {
    if (list.isEmpty()) {
      page = EMPTY_LIST;
    } else {
      int start = index * pageSize;
      int end = start + pageSize - 1;
      if (end >= list.size()) {
        end = list.size() - 1;
      }
      if (start >= list.size()) {
        index = 0;
        repaginate();
      } else if (start < 0) {
        index = list.size() / pageSize;
        if (list.size() % pageSize == 0) {
          index--;
        }
        repaginate();
      } else {
        page = list.subList(start, end + 1);
      }
    }
  }
  /* List accessors (uses page) */
  public int size() {
    return page.size();
  }
  public boolean isEmpty() {
    return page.isEmpty();
  }
  public boolean contains(Object o) {
    return page.contains(o);
  }
  public Iterator iterator() {
    return page.iterator();
  }
  public Object[] toArray() {
    return page.toArray();
  }
  public Object[] toArray(Object a[]) {
    return page.toArray(a);
  }
  public boolean containsAll(Collection c) {
    return page.containsAll(c);
  }
  public Object get(int index) {
    return page.get(index);
  }
  public int indexOf(Object o) {
    return page.indexOf(o);
  }
  public int lastIndexOf(Object o) {
    return page.lastIndexOf(o);
  }
  public ListIterator listIterator() {
    return page.listIterator();
  }
  public ListIterator listIterator(int index) {
    return page.listIterator(index);
  }
  public List subList(int fromIndex, int toIndex) {
    return page.subList(fromIndex, toIndex);
  }
  /* List mutators (uses master list) */
  public boolean add(Object o) {
    boolean b = list.add(o);
    repaginate();
    return b;
  }
  public boolean remove(Object o) {
    boolean b = list.remove(o);
    repaginate();
    return b;
  }
  public boolean addAll(Collection c) {
    boolean b = list.addAll(c);
    repaginate();
    return b;
  }
  public boolean addAll(int index, Collection c) {
    boolean b = list.addAll(index, c);
    repaginate();
    return b;
  }
  public boolean removeAll(Collection c) {
    boolean b = list.removeAll(c);
    repaginate();
    return b;
  }
  public boolean retainAll(Collection c) {
    boolean b = list.retainAll(c);
    repaginate();
    return b;
  }
  public void clear() {
    list.clear();
    repaginate();
  }
  public Object set(int index, Object element) {
    Object o = list.set(index, element);
    repaginate();
    return o;
  }
  public void add(int index, Object element) {
    list.add(index, element);
    repaginate();
  }
  public Object remove(int index) {
    Object o = list.remove(index);
    repaginate();
    return o;
  }
  /* Paginated List methods */
  public int getPageSize() {
    return pageSize;
  }
  public boolean isFirstPage() {
    return index == 0;
  }
  public boolean isMiddlePage() {
    return !(isFirstPage() || isLastPage());
  }
  public boolean isLastPage() {
    return list.size() - ((index + 1) * pageSize) < 1;
  }
  public boolean isNextPageAvailable() {
    return !isLastPage();
  }
  public boolean isPreviousPageAvailable() {
    return !isFirstPage();
  }
  public boolean nextPage() {
    if (isNextPageAvailable()) {
      index++;
      repaginate();
      return true;
    } else {
      return false;
    }
  }
  public boolean previousPage() {
    if (isPreviousPageAvailable()) {
      index--;
      repaginate();
      return true;
    } else {
      return false;
    }
  }
  public void gotoPage(int pageNumber) {
    index = pageNumber;
    repaginate();
  }
  public int getPageIndex() {
    return index;
  }
}
/*
 * Copyright 2004 Clinton Begin
 * 
 * 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.
 */
/**
 * Interface for lists that support paging
 * 
 */
interface PaginatedList extends List {
  /**
   * Returns the maximum number of items per page
   * 
   * @return The maximum number of items per page.
   */
  public int getPageSize();
  /**
   * Is the current page the first page?
   * 
   * @return True if the current page is the first page or if only a single page
   *         exists.
   */
  public boolean isFirstPage();
  /**
   * Is the current page a middle page (ie not first or last)?
   * 
   * @return True if the current page is not the first or last page, and more
   *         than one page exists (always returns false if only a single page
   *         exists).
   */
  public boolean isMiddlePage();
  /**
   * Is the current page the last page?
   * 
   * @return True if the current page is the last page or if only a single page
   *         exists.
   */
  public boolean isLastPage();
  /**
   * Is a page available after the current page?
   * 
   * @return True if the next page is available
   */
  public boolean isNextPageAvailable();
  /**
   * Is a page available before the current page?
   * 
   * @return True if the previous page is available
   */
  public boolean isPreviousPageAvailable();
  /**
   * Moves to the next page after the current page. If the current page is the
   * last page, wrap to the first page.
   * 
   * @return True if the page changed
   */
  public boolean nextPage();
  /**
   * Moves to the page before the current page. If the current page is the first
   * page, wrap to the last page.
   * 
   * @return True if the page changed
   */
  public boolean previousPage();
  /**
   * Moves to a specified page. If the specified page is beyond the last page,
   * wrap to the first page. If the specified page is before the first page,
   * wrap to the last page.
   * 
   * @param pageNumber
   *          The page to go to
   */
  public void gotoPage(int pageNumber);
  /**
   * Returns the current page index, which is a zero based integer. All
   * paginated list implementations should know what index they are on, even if
   * they don"t know the ultimate boundaries (min/max).
   * 
   * @return The current page
   */
  public int getPageIndex();
}

Paging over a collection

    
/*
 * Copyright (c) 2003-2006, Simon Brown
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in
 *     the documentation and/or other materials provided with the
 *     distribution.
 *
 *   - Neither the name of Pebble nor the names of its contributors may
 *     be used to endorse or promote products derived from this software
 *     without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
import java.util.List;
/**
 * Helper class that implements paging over a collection.
 *
 * @author    Simon Brown
 */
public class Pageable<T> {
  /** the default page size */
  public static final int DEFAULT_PAGE_SIZE = 10;
  private static final int PAGE_WINDOW = 10;
  /** the list over which this class is paging */
  private List<T> list;
  /** the page size */
  private int pageSize = DEFAULT_PAGE_SIZE;
  /** the current page */
  private int page;
  /** the starting index */
  private int startingIndex;
  /** the ending index */
  private int endingIndex;
  /** the maximum number of pages */
  private int maxPages;
  /**
   * Creates a new instance with the specified list.
   *
   * @param list    a List
   */
  public Pageable(List<T> list) {
    this.list = list;
    this.page = 1;
    this.maxPages = 1;
    calculatePages();
  }
  private void calculatePages() {
    if (pageSize > 0) {
      // calculate how many pages there are
      if (list.size() % pageSize == 0) {
        maxPages = list.size() / pageSize;
      } else {
        maxPages = (list.size() / pageSize) + 1;
      }
    }
  }
  /**
   * Gets the list that this instance is paging over.
   *
   * @return  a List
   */
  public List<T> getList() {
    return this.list;
  }
  /**
   * Gets the subset of the list for the current page.
   *
   * @return  a List
   */
  public List<T> getListForPage() {
    return list.subList(startingIndex, endingIndex);
  }
  /**
   * Gets the page size.
   *
   * @return  the page size as an int
   */
  public int getPageSize() {
    return this.pageSize;
  }
  /**
   * Sets the page size.
   *
   * @param pageSize   the page size as an int
   */
  public void setPageSize(int pageSize) {
    this.pageSize = pageSize;
    calculatePages();
  }
  /**
   * Gets the page.
   *
   * @return  the page as an int
   */
  public int getPage() {
    return this.page;
  }
  /**
   * Sets the page size.
   *
   * @param p    the page as an int
   */
  public void setPage(int p) {
    if (p >= maxPages) {
      this.page = maxPages;
    } else if (p <= 1) {
      this.page = 1;
    } else {
      this.page = p;
    }
    // now work out where the sub-list should start and end
    startingIndex = pageSize * (page-1);
    if (startingIndex < 0) {
      startingIndex = 0;
    }
    endingIndex = startingIndex + pageSize;
    if (endingIndex > list.size()) {
      endingIndex = list.size();
    }
  }
  /**
   * Gets the maximum number of pages.
   *
   * @return  the maximum number of pages as an int
   */
  public int getMaxPages() {
    return this.maxPages;
  }
  /**
   * Determines whether there is a previous page and gets the page number.
   *
   * @return  the previous page number, or zero
   */
  public int getPreviousPage() {
    if (page > 1) {
      return page-1;
    } else {
      return 0;
    }
  }
  /**
   * Determines whether there is a next page and gets the page number.
   *
   * @return  the next page number, or 0
   */
  public int getNextPage() {
    if (page < maxPages) {
      return page+1;
    } else {
      return 0;
    }
  }
  /**
   * Gets the minimum page in the window.
   *
   * @return  the page number
   */
  public int getMinPageRange() {
    if (getPage() > PAGE_WINDOW) {
      return getPage() - PAGE_WINDOW;
    } else {
      return 1;
    }
  }
  /**
   * Gets the maximum page in the window.
   *
   * @return  the page number
   */
  public int getMaxPageRange() {
    if (getPage() < (getMaxPages() - PAGE_WINDOW)) {
      return getPage() + PAGE_WINDOW;
    } else {
      return getMaxPages();
    }
  }
}