按对象中某一属性排序

来源：互联网发布：聊天有哪些软件编辑：程序博客网时间：2024/05/22 08:17

1.Comparable接口是在java.lang类中的，而Comparator接口是在java.util类中的。
2.Comparable 是在集合内部定义的方法实现的排序，Comparator 是在集合外部实现的排序，所以，如想实现排序，就需要在集合外定义 Comparator 接口的方法或在集合内实现 Comparable 接口的方法。

用自定义类实现 Comparable接口，那么这个类就具有排序功能，Comparable和具体你要进行排序的类的实例邦定。

而Comparator比较灵活，它没有和任何类绑定，实现它的自定义类仅仅定义了一种排序方式或排序规则。不言而喻，这种方式比较灵活。我们的要排序的类可以分别和多个实现 Comparator接口的类绑定，从而达到可以按自己的意愿实现按多种方式排序的目的。Comparable——“静态绑定排序”,Comparator——“动态绑定排序”。

排序：

 Collections.sort(lists, new comparator(){                         int compare(Object o1, Object o2) {             Member m1=(Member)o1;        Member m2=(Member)o2;                // 按姓名排序        return m1.getName().compareTo(m2.getName();   }   });

根据第一个参数小于、等于或大于第二个参数分别返回负整数、零或正整数

属性为String型：(动态加载对象属性的get方法)

   1. public class SortList<E>{      2.     public void Sort(List<E> list, final String method, final String sort){     3.         Collections.sort(list, new Comparator() {                4.             public int compare(Object a, Object b) {     5.                 int ret = 0;     6.                 try{     7.                     Method m1 = ((E)a).getClass().getMethod(method, null);     8.                     Method m2 = ((E)b).getClass().getMethod(method, null);     9.                     if(sort != null && "desc".equals(sort))//倒序    10.                         ret = m2.invoke(((E)b), null).toString().compareTo(m1.invoke(((E)a), null).toString());     11.                     else//正序    12.                         ret = m1.invoke(((E)a), null).toString().compareTo(m2.invoke(((E)b), null).toString());    13.                 }catch(NoSuchMethodException ne){    14.                     System.out.println(ne);    15.                 }catch(IllegalAccessException ie){    16.                     System.out.println(ie);    17.                 }catch(InvocationTargetException it){    18.                     System.out.println(it);    19.                 }    20.                 return ret;    21.             }    22.          });    23.     }    24. }

m1:

public java.lang.Integer com.openb2c.openreport.DayReport.getOrderSize()

完整连接：

1.http://wenku.baidu.com/view/a19a50ea81c758f5f61f674a.html

2.http://jardot.iteye.com/blog/762349

DayReport.java类：

public class DayReport extends BaseReport{private String date;private Double totalFee;private Double refundFee;private Double getMoney;private Double postFee;private Integer orderSize;private Long productNum;  //产品数，即符合条件的订单中有多少个产品private Integer backProductNum; //退款通过的订单中产品的个数private Integer backOrderNum;  //退款通过的订单个数public String getDate() {return date;}public void setDate(String date) {this.date = date;}public Double getTotalFee() {return totalFee;}public void setTotalFee(Double totalFee) {this.totalFee = totalFee;}public Double getRefundFee() {return refundFee;}public void setRefundFee(Double refundFee) {this.refundFee = refundFee;}public Double getGetMoney() {return getMoney;}public void setGetMoney(Double getMoney) {this.getMoney = getMoney;}public Double getPostFee() {return postFee;}public void setPostFee(Double postFee) {this.postFee = postFee;}public Integer getOrderSize() {return orderSize;}public void setOrderSize(Integer orderSize) {this.orderSize = orderSize;}public Long getProductNum() {return productNum;}public void setProductNum(Long productNum) {this.productNum = productNum;}public Integer getBackProductNum() {return backProductNum;}public void setBackProductNum(Integer backProductNum) {this.backProductNum = backProductNum;}public Integer getBackOrderNum() {return backOrderNum;}public void setBackOrderNum(Integer backOrderNum) {this.backOrderNum = backOrderNum;}}

1、对Double型数据排序（通用方法）：

/**     * 给Double型排序     * method 为DayReport中属性的 get方法名如：getOrderSize     * sort 为排序     *check 为选择的条件如1天内、1月内等     */@SuppressWarnings("unchecked")public static  void SortDouble (List<DayReport> list,final String method,final String sort){Comparator comparator = new Comparator(){public int compare(Object a, Object b) {int ret = 0;  try { Method m1 = ((DayReport)a).getClass().getMethod(method, null); Method m2 = ((DayReport)b).getClass().getMethod(method, null); double m=(Double) m1.invoke((DayReport)a); double n=(Double) m2.invoke((DayReport)b); double c=m-n;if(c>0.0)//倒序  {if(sort.equals("DESC")){ret=-1;  //本来}else{ret=1;}}else if(c<0.0){if(sort.equals("DESC")){ret=1;}else{ret=-1;}}else{ret=0;}} catch (SecurityException e) {StringBuilder msg = new StringBuilder("Double类型数据排序时出现异常！");Debug.logError(e,msg.toString(), module);} catch (NoSuchMethodException e) {StringBuilder msg = new StringBuilder("Double类型数据排序时出现异常！");Debug.logError(e,msg.toString(), module);} catch (IllegalAccessException e) {StringBuilder msg = new StringBuilder("Double类型数据排序时出现异常！");Debug.logError(e,msg.toString(), module);} catch (InvocationTargetException e) {StringBuilder msg = new StringBuilder("Double类型数据排序时出现异常！");Debug.logError(e,msg.toString(), module);}  return ret;}};Collections.sort(list,comparator);}

2.对Int型排序（通用方法）

/**     * 给int型排序     */@SuppressWarnings("unchecked")public static  void SortInt (List<DayReport> list,final String method,final String sort){/*Comparator comparator = new Comparator(){public int compare(Object a, Object b) {Integer aa = ((DayReport) a).getOrderSize();Integer bb = ((DayReport) b).getOrderSize();Integer cc = aa - bb;if (cc > 0)return 1;if (cc < 0)return -1;elsereturn 0;}};Collections.sort(list,comparator);}*/Comparator comparator = new Comparator() {public int compare(Object a, Object b) {int ret = 0;Method m1 = ((DayReport) a).getClass().getMethod(method,null);Method m2 = ((DayReport) b).getClass().getMethod(method,null);Integer m = (Integer) m1.invoke((DayReport) a);Integer n = (Integer) m2.invoke((DayReport) b);Integer c = m - n;if (c > 0)// 倒序{if (sort.equals("DESC")) {ret = -1; // 本来} else {ret = 1;}} else if (c < 0) {if (sort.equals("DESC")) {ret = 1;} else {ret = -1;}} else {ret = 0;}return ret;}};Collections.sort(list, comparator);}

使用：

<th><a href="<@ofbizUrl>queryDay?check=${check?if_exists}&method=getTotalFee&sort=${orderby?if_exists}</@ofbizUrl>">销售额</a></th>          <th><a href="<@ofbizUrl>queryDay?check=${check?if_exists}&method=getRefundFee&sort=${orderby?if_exists}</@ofbizUrl>">退款额</a></th>

String method=(String)context.get("method");        String  sort=(String)context.get("sort");        if(UtilValidate.isEmpty(sort)){            sort="ASC";    }else{if (UtilValidate.areEqual(sort, "ASC")) {sort = "DESC";} else {sort = "ASC";}    }                if(UtilValidate.isNotEmpty(method)){          if(method.equals("getOrderSize")){        DayReportService.SortInt(finallyList,method,sort);        }else{        DayReportService.SortDouble(finallyList,method,sort);        }        }  result.put("finallyList", finallyList);result.put("sort", sort);result.put("check", check);

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