Java8 List去重（单属性或组合属性）

package com.demo.jdk8.collectors;
 
import com.google.common.collect.Lists;
import org.junit.jupiter.api.Test;
 
import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.TreeSet;
import java.util.stream.Collectors;
 
/**
 * @author Shanks
 * @date 2018-10-15
 */
public class CollectingAndThenTest {
 
    @Test
    void testCollectingAndThen() {
 
        UserOrder order0 = new UserOrder("年会", "张三", "box0001");
        UserOrder order1 = new UserOrder("婚庆", "张三", "box0002");
        UserOrder order2 = new UserOrder("旅游", "李四", "box0003");
        UserOrder order3 = new UserOrder("发布会", "张三", "box0002");
        UserOrder order4 = new UserOrder("旅游", "李四", "box0004");
 
        List<UserOrder> list = Lists.newArrayList(order0, order1, order2, order3, order4);
 
        System.out.println("=====>只根据单一属性photographerName进行去重");
        // <R, A> R collect(Collector<? super T, A, R> collector);
        // collectingAndThen(Collector<T, A, R> downstream, Function<R, RR> finisher)
        // toCollection(Supplier<C> collectionFactory)
        ArrayList<UserOrder> distinctByName = list.stream()
                .collect(
                        Collectors.collectingAndThen(
                                Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(UserOrder::getPhotographerName))),
                                userOrders -> new ArrayList<>(userOrders)
                        )
                );
        distinctByName.forEach(System.out::println);
 
        System.out.println("=====>同时根据photographerName和deviceCode两个属性进行去重");
        ArrayList<UserOrder> distinctByNameAndCode = list.stream()
                .collect(
                        Collectors.collectingAndThen(
                                Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(userOrder -> userOrder.getPhotographerName() + userOrder.getDeviceCode()))),
                                ArrayList::new
                        )
                );
        distinctByNameAndCode.forEach(System.out::println);
    }
}

打印结果：

=====>只根据单一属性photographerName进行去重
UserOrder{shootingTheme='年会', photographerName='张三', deviceCode='box0001'}
UserOrder{shootingTheme='旅游', photographerName='李四', deviceCode='box0003'}
 
=====>同时根据photographerName和deviceCode两个属性进行去重
UserOrder{shootingTheme='年会', photographerName='张三', deviceCode='box0001'}
UserOrder{shootingTheme='婚庆', photographerName='张三', deviceCode='box0002'}
UserOrder{shootingTheme='旅游', photographerName='李四', deviceCode='box0003'}
UserOrder{shootingTheme='旅游', photographerName='李四', deviceCode='box0004'}

实体类：

package com.demo.jdk8.collectors;
 
/**
 * @author Shanks
 * @date 2018-10-16
 */
public class UserOrder {
 
    /**
     * 拍摄主题
     */
    private String shootingTheme;
    /**
     * 摄影师
     */
    private String photographerName;
    /**
     * 设备编号
     */
    private String deviceCode;
 
    public UserOrder() {
    }
 
    public UserOrder(String shootingTheme, String photographerName, String deviceCode) {
        this.shootingTheme = shootingTheme;
        this.photographerName = photographerName;
        this.deviceCode = deviceCode;
    }
 
    @Override
    public String toString() {
        return "UserOrder{" +
                "shootingTheme='" + shootingTheme + '\'' +
                ", photographerName='" + photographerName + '\'' +
                ", deviceCode='" + deviceCode + '\'' +
                '}';
    }
 
    public String getShootingTheme() {
        return shootingTheme;
    }
 
    public void setShootingTheme(String shootingTheme) {
        this.shootingTheme = shootingTheme;
    }
 
    public String getPhotographerName() {
        return photographerName;
    }
 
    public void setPhotographerName(String photographerName) {
        this.photographerName = photographerName;
    }
 
    public String getDeviceCode() {
        return deviceCode;
    }
 
    public void setDeviceCode(String deviceCode) {
        this.deviceCode = deviceCode;
    }
}