JAVA JDK8 List分组的实现和用法

JAVA JDK8 List分组的实现和用法分组的实现和用法

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概述概述

对List进行分组是日常开发中，经常遇到的，在JDK 8中对List按照某个属性分组的代码，超级简单。

package test;

import com.alibaba.fastjson.JSON;

import com.alibaba.fastjson.serializer.SerializerFeature;

List<Coupon> couponList = new ArrayList<>();

Coupon coupon1 = new Coupon(1,100,"优惠券1");

Coupon coupon2 = new Coupon(2,200,"优惠券2");

Coupon coupon3 = new Coupon(3,300,"优惠券3");

Coupon coupon4 = new Coupon(3,400,"优惠券4");

couponList.add(coupon1);

couponList.add(coupon2);

couponList.add(coupon3);

couponList.add(coupon4);

Map<Integer, List<Coupon>> resultList = couponList.stream().collect(Collectors.groupingBy(Coupon::getCouponId));

private Integer price;

private String name;

public Coupon(Integer couponId, Integer price, String name) {

this.couponId = couponId;

this.price = price;

this.name = name;

}

public Integer getCouponId() {

return couponId;

}

public void setPrice(Integer price) {

this.price = price;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

}

"price":100

}

],

2:[

{

"couponId":2,

"name":"优惠券2",

"price":200

}

],