List集合中的对象按照某个字段去重实现

package com.liying.banana.user;

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;

import com.liying.banana.order.vo.OrderVO;

/**
 * List集合中的对象按照某个字段去重实现
 *
 * @author jqlin
 *
 */
public class DuplicateOrderTest {
    public static void main(String[] args) {
        List<OrderVO> orderList = new ArrayList<OrderVO>();
        OrderVO orderVO = new OrderVO();
        orderVO.setOrderNo("11");
        orderVO.setUserId("aa");
        orderList.add(orderVO);

        orderVO = new OrderVO();
        orderVO.setOrderNo("22");
        orderVO.setUserId("bb");
        orderList.add(orderVO);

        orderVO = new OrderVO();
        orderVO.setOrderNo("33");
        orderVO.setUserId("aa");
        orderList.add(orderVO);

        List<OrderVO> dataList = removeDuplicateOrder(orderList);
        for(OrderVO data : dataList){
            System.out.println(data.getOrderNo() + ":" + data.getUserId());
        }
    }

    /**
     * 去重
     *
     * @param orderList
     * @return
     * @author jqlin
     */
    private static List<OrderVO> removeDuplicateOrder(List<OrderVO> orderList) {
        Set<OrderVO> set = new TreeSet<OrderVO>(new Comparator<OrderVO>() {
            @Override
            public int compare(OrderVO a, OrderVO b) {
                // 字符串则按照asicc码升序排列
                return a.getUserId().compareTo(b.getUserId());
            }
        });

        set.addAll(orderList);
        return new ArrayList<OrderVO>(set);
    }
}

执行结果：

11:aa
22:bb