List多个字段排序、去重

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 {

	@Override
	public 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 removeRepeat(List all,List sub){
		if (all.size()==0 && sub.size()!=0) {
			return sub;
		}
		for (CompanyData companyData : sub) {
			all.add(companyData);
		}
		Set set = new HashSet();  
		List newList = new ArrayList();  
		for (Iterator 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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