List多个字段排序、去重

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1、List多个字段排序

List集合排序是通过java.util.Collections中的sort方法实现的，我们现在的业务场景是：根据List集合中实体bean里面的多个属性字段排序

首先写一个sort方法的比较器MyComparator

public class MyComparator  implements Comparator<Object> {@Overridepublic int compare(Object o1, Object o2) {CompanyData com1 = (CompanyData) o1;CompanyData com2 = (CompanyData) o2;if (com1.getMemlevel().compareTo(com2.getMemlevel()) != 0){ //如果会员等级不一样        return com1.getMemlevel().compareTo(com2.getMemlevel());} else if (com1.getCreditLevel().compareTo(com2.getCreditLevel())!=0) {//如果信用等级不一样     return com1.getCreditLevel().compareTo(com2.getCreditLevel());} else {//按积分return com1.getIntegral().compareTo(com2.getIntegral());}}}

然后调用排序

//按会员等级、信用等级、积分排序Collections.sort( list, new MyComparator());

2、list集合去重

//去掉重复public List<CompanyData> removeRepeat(List<CompanyData> all,List<CompanyData> sub){if (all.size()==0 && sub.size()!=0) {return sub;}for (CompanyData companyData : sub) {all.add(companyData);}Set<Integer> set = new HashSet<Integer>();  List<CompanyData> newList = new ArrayList<CompanyData>();  for (Iterator<CompanyData> iter = all.iterator(); iter.hasNext();) {  CompanyData element = (CompanyData) iter.next();         if (set.add(element.getBelong()))             newList.add(element);      }      return newList;  }

因为set集合只能添加不重复的元素，根据这个特点可以排除掉list集合中的重复元素

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