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  

1. package com;  
2.   
3. interface Operation {  
4.     double operateTwoIntNum(int a, int b);  
5. }  
6.   
7. public class InnerClassTest {  
8.   
9.     /** 
10.      * 加法 
11.      */  
12.     public static double add(int a, int b) {  
13.         /** 
14.          * 匿名内部类实现加法 
15.          */  
16.         double c = new Operation() {  
17.   
18.             @Override  
19.             public double operateTwoIntNum(int a, int b) {  
20.   
21.                 return a + b;  
22.             }  
23.         }.operateTwoIntNum(a, b);  
24.         return c;  
25.     }  
26.   
27.     /** 
28.      * 减法 
29.      * @param a 
30.      * @param b 
31.      * @return 
32.      */  
33.     public static double subtract(int a, int b) {  
34.         /** 
35.          * 匿名内部类实现加法 
36.          */  
37.         double c = new Operation() {  
38.   
39.             @Override  
40.             public double operateTwoIntNum(int a, int b) {  
41.                 // TODO Auto-generated method stub  
42.                 return a - b;  
43.             }  
44.         }.operateTwoIntNum(a, b);  
45.         return c;  
46.     }  
47.   
48.     public static void main(String[] args) {  
49.        System.out.println(add(10, 3));  
50.        System.out.println(subtract(10, 3));  
51.     }  
52. }  

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() {@Overridepublic 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() {@Overridepublic double operateTwoIntNum(int a, int b) {// TODO Auto-generated method stubreturn 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  

1. public interface LinkBuilder {  
2.     public StringBuffer getPagerUrl();  
3.     //public void setPage(int page);  
4.       
5.     public StringBuffer getPageUrl(int page);  
6. }  
7.   
8.   
9. public abstract class AbstractLinkBuilder implements LinkBuilder {  
10.   
11.     @Override  
12.     public final StringBuffer getPageUrl(int page) {  
13.         StringBuffer url = new StringBuffer(XssFilterService.dhtmlSpecialchars(  
14.                 this.getPagerUrl(), true));  
15.         if (url.toString().indexOf("?") > 0) {  
16.             url.append("&");  
17.         } else {  
18.             url.append("?");  
19.         }  
20.         url.append("page=").append(page);  
21.         return url;  
22.     }  
23.   
24. }  
25.   
26.   
27.     Pager pager = Pager.register("newPagerWidget",new AbstractLinkBuilder() {@Override  
28.                         public StringBuffer getPagerUrl() {  
29.                             StringBuffer url = null;  
30.                             if (queryAgentStore != null) {  
31.   
32.                                 url = new StringBuffer("agentstorelist.html?");  
33.                                 if (StringUtils.isNotBlank(queryAgentStore  
34.                                         .getStoreName()))// 店铺关键字  
35.                                 {  
36.                                     url.append("&queryAgentStore.storeName="+ XssFilterService.dhtmlSpecialchars(queryAgentStore.getStoreName()));  
37.                                 }  
38.                                 if (queryAgentStore.getCity()!=null)// 城市编码  
39.                                 {  
40.                                     url.append("&queryAgentStore.city="+ queryAgentStore.getCity());  
41.                                 }  
42.                                 if(orderByClause!=null&&!"".equals(orderByClause))  
43.                                 {  
44.                                     url.append("&orderByClause="+orderByClause);  
45.                                 }  
46.                             } else {  
47.                                 url = new StringBuffer("agentstorelist.html");  
48.                             }  
49.                             return url;  
50.                         }  
51.   
52.                     }, request);  
53.   
54. public class Pager  
55. {  
56. public Pager(LinkBuilder builder) {  
57.         this.linkBuilder = builder;  
58.     }  
59. public String getUrl(int page) {  
60.         return staticTool.process(this.linkBuilder.getPageUrl(page).toString());  
61.     }  
62.   
63. }  

public interface LinkBuilder {public StringBuffer getPagerUrl();//public void setPage(int page);public StringBuffer getPageUrl(int page);}public abstract class AbstractLinkBuilder implements LinkBuilder {@Overridepublic 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() {@Overridepublic 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());}}