http://java.sun.com/docs/books/tutorial/jmx/remote/custom.html

非常不错的实例.

很齐全，比国内网络上断章取义的文章好的多。

/**
				* @author Fred Zhu
				* 分页辅助工具
				*/
				public class PageBean {

				private int currentPage = 1;// 当前页数
				private int totalPages = 0;// 总页数
				private int pageSize = 0;// 每页显示数
				private int totalRows = 0;// 总数据数
				private int startNum = 0;// 开始记录
				private int endNum = pageSize;//结束记录
				private int nextPage = 0;// 下一页
				private int previousPage = 0;// 上一页
				private boolean hasNextPage = false;// 是否有下一页
				private boolean hasPreviousPage = false;// 是否有前一页

				public PageBean(int pageSize, int currentPage, int totalRows) {

				this.pageSize = pageSize;
				this.currentPage = currentPage;
				this.totalRows = totalRows;

				//计算总页数
				if ((totalRows % pageSize) == 0) {
				totalPages = totalRows / pageSize;
				} else {
				totalPages = totalRows / pageSize + 1;
				}

				//是否有下一页
				if (currentPage >= totalPages) {
				hasNextPage = false;
				currentPage = totalPages;
				} else {
				hasNextPage = true;
				}

				//是否有上一页
				if (currentPage <= 1) {
				hasPreviousPage = false;
				currentPage = 1;
				} else {
				hasPreviousPage = true;
				}

				startNum = (currentPage - 1) * pageSize;//开始记录数

				if(totalPages-currentPage<1){
				endNum = totalRows;
				}else{
				endNum = currentPage*pageSize;
				}

				nextPage = currentPage + 1;//下一页页码

				previousPage = currentPage - 1;//上一页页码

				if (nextPage >= totalPages) {
				nextPage = totalPages;
				}

				if (previousPage <= 1) {
				previousPage = 1;
				}

				}

				public void refresh(int currentPage){
				this.currentPage = currentPage;
				startNum = (currentPage - 1) * pageSize;
				if(totalPages-currentPage<1){
				endNum = totalRows;
				}else{
				endNum = currentPage*pageSize;
				}
				}

				public boolean isHasNextPage() {

				return hasNextPage;

				}

				public boolean isHasPreviousPage() {

				return hasPreviousPage;

				}

				/**
				* @return the nextPage
				*/
				public int getNextPage() {
				return nextPage;
				}

				/**
				* @param nextPage
				*             the nextPage to set
				*/
				public void setNextPage(int nextPage) {
				this.nextPage = nextPage;
				}

				/**
				* @return the previousPage
				*/
				public int getPreviousPage() {
				return previousPage;
				}

				/**
				* @param previousPage
				*             the previousPage to set
				*/
				public void setPreviousPage(int previousPage) {
				this.previousPage = previousPage;
				}

				/**
				* @return the currentPage
				*/
				public int getCurrentPage() {
				return currentPage;
				}

				/**
				* @param currentPage
				*             the currentPage to set
				*/
				public void setCurrentPage(int currentPage) {
				this.currentPage = currentPage;
				}

				/**
				* @return the pageSize
				*/
				public int getPageSize() {
				return pageSize;
				}

				/**
				* @param pageSize
				*             the pageSize to set
				*/
				public void setPageSize(int pageSize) {
				this.pageSize = pageSize;
				}

				/**
				* @return the totalPages
				*/
				public int getTotalPages() {
				return totalPages;
				}

				/**
				* @param totalPages
				*             the totalPages to set
				*/
				public void setTotalPages(int totalPages) {
				this.totalPages = totalPages;
				}

				/**
				* @return the totalRows
				*/
				public int getTotalRows() {
				return totalRows;
				}

				/**
				* @param totalRows
				*             the totalRows to set
				*/
				public void setTotalRows(int totalRows) {
				this.totalRows = totalRows;
				}

				/**
				* @param hasNextPage
				*             the hasNextPage to set
				*/
				public void setHasNextPage(boolean hasNextPage) {
				this.hasNextPage = hasNextPage;
				}

				/**
				* @param hasPreviousPage
				*             the hasPreviousPage to set
				*/
				public void setHasPreviousPage(boolean hasPreviousPage) {
				this.hasPreviousPage = hasPreviousPage;
				}

				/**
				* @return the startNum
				*/
				public int getStartNum() {
				return startNum;
				}

				/**
				* @param startNum
				*             the startNum to set
				*/
				public void setStartNum(int startNum) {
				this.startNum = startNum;
				}

				public int getEndNum() {
				return endNum;
				}

				public void setEndNum(int endNum) {
				this.endNum = endNum;
				}
				}

原文：http://www.javaeye.com/topic/569993

对于常见业务方法返回List对象时一般有二种方法：

1、返回含数据的数据的List对象，该对象可能为空

2、返回null

如下方法：

一般使用时，

这时候list都将具体指向一个内存，如果返回值为空时，list指向一个null的空内存，这时我们又要对list进行是否为null进行判断，量大时就可能对程序造成瓶颈。文章作者的解决方法是用Collections工具类的empty系列静态方法解决。

既如下代码：

此时如果为空返回的list将不存在为null的可能，并且empty系列方法是静态方法，所有引用都指向静态内存，不会生产和占用新的资源。不失为一个好的方法。

我们也可以自己编写自己的empty静态类，既每次都返回为空的静态的List、Map….对象。

我自己的一些理解，详细情况请大家访问原文和作者交流。

最近，因工作需要对JMS进行了些了解和学习。不敢藏私，把些许经验和大家分享下，顺带自己也总结下，如有不足请指出。学习ActiveMq首先要对JMS规范有所了解。

JMS教程 这篇文章介绍的挺不错，虽然也是转载的不过好在排版还可以！呵呵！

要进行ActiveMq的开发，除了对概念要有所了解外，还要对JMS常用的接口有所了解，上面文档里也有描述。

下面2个程序，一个是向ActiveMq发送JMS消息，另一个是从ActiveMq里读取JMS消息！

package cn.fengsage.jms;

import java.util.Hashtable;

import javax.jms.*;

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;

/**
* @author Fred Zhu
*
*/
public class SenderTest {

private static final String DistDestQueName = "test";
private static final String JMS_FACTORY = "ConnectionFactory";

private Context jndiContext = null;
private QueueConnectionFactory qconFactory = null;
private QueueConnection qconn = null;
private QueueSession qsession = null;
private Queue queueDest = null;
private QueueSender qsender = null;

public void sendMessage(String msg) throws NamingException, JMSException {
jndiContext = this.getJndiContext();
qconFactory = (QueueConnectionFactory) jndiContext.lookup(JMS_FACTORY);
qconn = qconFactory.createQueueConnection();
qsession = qconn.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);
queueDest = (Queue) jndiContext.lookup(DistDestQueName);
qsender = qsession.createSender(queueDest);
TextMessage objMsg = null;
objMsg = qsession.createTextMessage();
qconn.start();
objMsg.setText(msg);
qsender.send(objMsg);
qconn.close();
qsender.close();

}

private Context getJndiContext() throws NamingException {
Hashtable properties = new Hashtable();
properties.put(Context.INITIAL_CONTEXT_FACTORY,
"org.apache.activemq.jndi.ActiveMQInitialContextFactory");
properties.put(Context.PROVIDER_URL, "tcp://localhost:61616");
return new InitialContext(properties);
}

public static void main(String[] args) throws NamingException, JMSException {
SenderTest test = new SenderTest();
test.sendMessage("jms test");

}
}

package cn.fengsage.jms;

import java.util.Hashtable;

import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.Queue;
import javax.jms.QueueConnection;
import javax.jms.QueueConnectionFactory;
import javax.jms.QueueReceiver;
import javax.jms.QueueSender;
import javax.jms.QueueSession;
import javax.jms.Session;
import javax.jms.TextMessage;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;

/**
* @author Fred Zhu
*
*/
public class ReceiveTest {
private static final String DistDestQueName = "test";
private static final String JMS_FACTORY = "ConnectionFactory";

private Context jndiContext = null;
private QueueConnectionFactory qconFactory = null;
private QueueConnection qconn = null;
private QueueSession qsession = null;
private Queue queueDest = null;
private QueueReceiver qreceiver = null;

public void reveiveMessage() throws NamingException, JMSException {
jndiContext = this.getJndiContext();
qconFactory = (QueueConnectionFactory) jndiContext.lookup(JMS_FACTORY);
qconn = qconFactory.createQueueConnection();
qsession = qconn.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);
queueDest = (Queue) jndiContext.lookup(DistDestQueName);
qreceiver = qsession.createReceiver(queueDest);
qconn.start();
TextMessage message = (TextMessage) qreceiver.receive();
System.out.println(message.getText());
qconn.close();

}

private Context getJndiContext() throws NamingException {
Hashtable properties = new Hashtable();
properties.put(Context.INITIAL_CONTEXT_FACTORY,
"org.apache.activemq.jndi.ActiveMQInitialContextFactory");
properties.put(Context.PROVIDER_URL, "tcp://localhost:61616");
return new InitialContext(properties);
}

public static void main(String[] args) throws NamingException, JMSException {
ReceiveTest test = new ReceiveTest();
test.reveiveMessage();
}
}

补充个官方的例子：http://activemq.apache.org/jndi-support.html