List集合中的对象按照某个字段去重实现

package com.bean.user;

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

import com.bean.Order;

/**
* List集合中的对象按照某个字段去重实现
*

*
*/
public class DuplicateOrderTest {
    public static void main(String[] args) {
        List<Order> orderList = new ArrayList<Order>();
        Order order = new Order();
        order.setOrderNo("123");
        order.setUserId("aa123");
        orderList.add(order);

       order = new Order();
        order.setOrderNo("123");
        order.setUserId("bb123");
        orderList.add(order);

         order = new Order();
        order.setOrderNo("33");
        order.setUserId("aa123");
        orderList.add(order);
       
        List<Order> dataList = removeDuplicateOrder(orderList);
        for(Order data : dataList){
            System.out.println(data.getOrderNo() + ":" + data.getUserId());
        }
    }

    /**
     * 去重
     * @param orderList
     * @return
     */
    private static List<Order> removeDuplicateOrder(List<Order> orderList) {
        Set<Order> set = new TreeSet<Order>(new Comparator<Order>() {
            public int compare(Order a, Order 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<Order>(set);
    }
}




执行结果：

123:aa123
33:aa123