将一个list对象数组按照指定的规则排序

淩亂°似流年 2022-07-13 19:39 246阅读 0赞

方法一

import java.util.Collections;
    import java.util.Comparator;
    import java.util.List;
    
    import com.google.common.base.Function;
    import com.google.common.collect.Lists;
    
    public PageInfo<Member> findPage(Long styleId,Integer pageNum, Integer pageSize) {
    	PageHelper.startPage(pageNum, pageSize);
    	MemberDesignerBean memberDesignerBean = new MemberDesignerBean();
    	memberDesignerBean.setStyleId(styleId);
    	List<MemberDesigner> list = memberDesignerDao.list(memberDesignerBean);
    	if(CollectionUtils.isEmpty(list)){
    		return null;
    	}
    	PageInfo<MemberDesigner> pageInfo = new PageInfo<MemberDesigner>(list);
    
    	//将一个List<MemberDesigner>中的id单独提取出来。这个id在数组中是有序的，在后面需要用到。
    	final List<Long> idList = Lists.transform(list, new Function<MemberDesigner, Long>() {
    		@Override
    		public Long apply(MemberDesigner input) {
    			return input.getMemberId();
    		}
    	});
    
    	//得到一个无序的List<Member>，按照上面的idList进行排序。
    	List<Member> designers = memberDao.listByIdList(idList);
    	Collections.sort(designers, new Comparator<Member>(){
    		@Override
    		public int compare(Member o1, Member o2) {
    			if (o1 == null) {
    				return -1;
    			} else if (o2 == null) {
    				return 1;
    			}
    			int s1index = idList.indexOf(o1.getId());
    			int s2index = idList.indexOf(o2.getId());
    			return s1index > s2index ? 1 : -1;
    		}});
    	
    	return PageInfoUtil.buildNewPageInfo(pageInfo, designers);
    }

方法二

import org.apache.commons.beanutils.BeanComparator;
    import org.apache.commons.collections.comparators.FixedOrderComparator;
    
    public PageInfo<Member> findPage(Long styleId,Integer pageNum, Integer pageSize) {
    	PageHelper.startPage(pageNum, pageSize);
    	MemberDesignerBean memberDesignerBean = new MemberDesignerBean();
    	memberDesignerBean.setStyleId(styleId);
    	List<MemberDesigner> list = memberDesignerDao.list(memberDesignerBean);
    	if(CollectionUtils.isEmpty(list)){
    		return null;
    	}
    	PageInfo<MemberDesigner> pageInfo = new PageInfo<MemberDesigner>(list);
    	List<Long> idList = BizUtil.extractToList(list, "memberId");
    	List<Member> designers = memberDao.listByIdList(idList);
    	designers = BizUtil.sortList("id", designers, idList);
    	return PageInfoUtil.buildNewPageInfo(pageInfo, designers);
    }	
    
    /**
     * list根据某个属性给定的集合排序
     * 
     * @param propertyName 属性名
     * @param list 需要排序的list
     * @param from 属性对应的集合值
     * @return list 排序后的list
     *
     */
    public static <T,F> List<T> sortList(String propertyName, List<T> list,List<F> from) {
    	FixedOrderComparator fixedOrderComparator = new FixedOrderComparator(from);
    	Comparator<T> comparator = new BeanComparator<T>(propertyName,fixedOrderComparator);
    	Collections.sort(list,comparator);
    	return list;
    }