编程技巧整理

1 数据库层或者逻辑层执行查询集合，如果null可以返回 Collections.empty_list,这样调用者就不必判断是不是为null

2 对某种操作查询加入延时动作

protected static class JMXConnectorCatcher implements Callable< JMXConnector >{

private final IJMXProtocolProvider provider;
private final ASNode node;
private final ExecutorService executor;

public JMXConnectorCatcher( final IJMXProtocolProvider provider, final ASNode node ){
this.provider = provider;
this.node = node;
this.executor = Executors.newCachedThreadPool( );
}

public JMXConnector call( ) throws Exception{
return this.provider.getJMXConnector( this.node );
}

public JMXConnector getConnector( ) throws Exception{
if( !this.executor.isShutdown( ) ){
final Future< JMXConnector > future = this.executor.submit( this );
final JMXConnector connector = future.get( 10, TimeUnit.SECONDS );
this.executor.shutdown( );
return connector;
}
return null;
}

}

内部类示例一：

Java代码






package com;

interface Operation {
double operateTwoIntNum(int a, int b);
}

public class InnerClassTest {

/**
* 加法
*/
public static double add(int a, int b) {
/**
* 匿名内部类实现加法
*/
double c = new Operation() {

@Override
public double operateTwoIntNum(int a, int b) {

return a + b;
}
}.operateTwoIntNum(a, b);
return c;
}

/**
* 减法
* @param a
* @param b
* @return
*/
public static double subtract(int a, int b) {
/**
* 匿名内部类实现加法
*/
double c = new Operation() {

@Override
public double operateTwoIntNum(int a, int b) {
// TODO Auto-generated method stub
return a - b;
}
}.operateTwoIntNum(a, b);
return c;
}

public static void main(String[] args) {
System.out.println(add(10, 3));
System.out.println(subtract(10, 3));
}
}

package com;

interface Operation {
double operateTwoIntNum(int a, int b);
}

public class InnerClassTest {

/**
* 加法
*/
public static double add(int a, int b) {
/**
* 匿名内部类实现加法
*/
double c = new Operation() {

@Override
public double operateTwoIntNum(int a, int b) {

return a + b;
}
}.operateTwoIntNum(a, b);
return c;
}

/**
* 减法
* @param a
* @param b
* @return
*/
public static double subtract(int a, int b) {
/**
* 匿名内部类实现加法
*/
double c = new Operation() {

@Override
public double operateTwoIntNum(int a, int b) {
// TODO Auto-generated method stub
return a - b;
}
}.operateTwoIntNum(a, b);
return c;
}

public static void main(String[] args) {
System.out.println(add(10, 3));
System.out.println(subtract(10, 3));
}
}

示例二：

这是我们工程中匿名内部类在分页方法中的运用，动态拼接分页链接地址：

Java代码






public interface LinkBuilder {
public StringBuffer getPagerUrl();
//public void setPage(int page);

public StringBuffer getPageUrl(int page);
}

public abstract class AbstractLinkBuilder implements LinkBuilder {

@Override
public final StringBuffer getPageUrl(int page) {
StringBuffer url = new StringBuffer(XssFilterService.dhtmlSpecialchars(
this.getPagerUrl(), true));
if (url.toString().indexOf("?") > 0) {
url.append("&");
} else {
url.append("?");
}
url.append("page=").append(page);
return url;
}

}

Pager pager = Pager.register("newPagerWidget",new AbstractLinkBuilder() {@Override
public StringBuffer getPagerUrl() {
StringBuffer url = null;
if (queryAgentStore != null) {

url = new StringBuffer("agentstorelist.html?");
if (StringUtils.isNotBlank(queryAgentStore
.getStoreName()))// 店铺关键字
{
url.append("&queryAgentStore.storeName="+ XssFilterService.dhtmlSpecialchars(queryAgentStore.getStoreName()));
}
if (queryAgentStore.getCity()!=null)// 城市编码
{
url.append("&queryAgentStore.city="+ queryAgentStore.getCity());
}
if(orderByClause!=null&&!"".equals(orderByClause))
{
url.append("&orderByClause="+orderByClause);
}
} else {
url = new StringBuffer("agentstorelist.html");
}
return url;
}

}, request);

public class Pager
{
public Pager(LinkBuilder builder) {
this.linkBuilder = builder;
}
public String getUrl(int page) {
return staticTool.process(this.linkBuilder.getPageUrl(page).toString());
}

}

public interface LinkBuilder {
public StringBuffer getPagerUrl();
//public void setPage(int page);

public StringBuffer getPageUrl(int page);
}

public abstract class AbstractLinkBuilder implements LinkBuilder {

@Override
public final StringBuffer getPageUrl(int page) {
StringBuffer url = new StringBuffer(XssFilterService.dhtmlSpecialchars(
this.getPagerUrl(), true));
if (url.toString().indexOf("?") > 0) {
url.append("&");
} else {
url.append("?");
}
url.append("page=").append(page);
return url;
}

}

Pager pager = Pager.register("newPagerWidget",new AbstractLinkBuilder() {@Override
public StringBuffer getPagerUrl() {
StringBuffer url = null;
if (queryAgentStore != null) {

url = new StringBuffer("agentstorelist.html?");
if (StringUtils.isNotBlank(queryAgentStore
.getStoreName()))// 店铺关键字
{
url.append("&queryAgentStore.storeName="+ XssFilterService.dhtmlSpecialchars(queryAgentStore.getStoreName()));
}
if (queryAgentStore.getCity()!=null)// 城市编码
{
url.append("&queryAgentStore.city="+ queryAgentStore.getCity());
}
if(orderByClause!=null&&!"".equals(orderByClause))
{
url.append("&orderByClause="+orderByClause);
}
} else {
url = new StringBuffer("agentstorelist.html");
}
return url;
}

}, request);

public class Pager
{
public Pager(LinkBuilder builder) {
this.linkBuilder = builder;
}
public String getUrl(int page) {
return staticTool.process(this.linkBuilder.getPageUrl(page).toString());
}

}