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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();
}
}
}
