Java 如何在对相似元素求和后获得列表
我有一个具有以下属性的产品类别列表:Java 如何在对相似元素求和后获得列表,java,list,arraylist,collections,Java,List,Arraylist,Collections,我有一个具有以下属性的产品类别列表: public class Products{ private int month; private int year; private int sku; private String detail; private Double quantity; private Double price; private Double discount; private Double %discount; // getters and setters stat
public class Products{
private int month;
private int year;
private int sku;
private String detail;
private Double quantity;
private Double price;
private Double discount;
private Double %discount;
// getters and setters
static List<Products> sumProduct(List<Products> itemList) {
List<Product> tempListP = new ArrayList<Product>();
Collections.sort(itemList, Comparator.comparing(Product::getYear)
.thenComparing(Product::getMonth).thenComparing(Product::getSku));
Integer itemCode = null;
double quantiti = 0;
double price = 0;
double discount = 0;
double %discount = 0;
Products itemObj = null;
Integer itemMonth= null;
Integer itemYear= null;
for (int i = 0; i < itemList.size(); i++) {
if (itemCode == null || (itemCode.equals(itemList.get(i).getSku()) && itemMonth.equals(itemList.get(i).getMonth()) && itemMonth.equals(itemList.get(i).getYear()) )) {
quantiti = quantiti + itemList.get(i).getquantiti();
price = price + itemList.get(i).getprice();
discount = discount + itemList.get(i).getdiscount();
%discount = %discount + itemList.get(i).get%discount();
itemMonth = itemList.get(i).getMonth();
itemYea = itemList.get(i).getYear();
} else {
itemObj = new Product( itemList.get(i).getMonth(), itemList.get(i).getYear(), itemCode, "" , quantiti, price,discount,%discount);
if (tempListP.contains(itemObj)) {
tempListP.remove(itemObj);
}
tempListP.add(itemObj);
quantiti = 0;
quantiti = quantiti + itemList.get(i).getquantiti();
price = 0;
price = price + itemList.get(i).getprice();
discount = 0;
discount = discount + itemList.get(i).getdiscount();
%discount = 0;
%discount = %discount + itemList.get(i).get%discount();
itemMonth = itemList.get(i).getMonth();
itemYea = itemList.get(i).getYear();
}
itemCode = itemList.get(i).getSku();
if (i == itemList.size() - 1) {
itemObj = new Product( itemList.get(i).getMonth(), itemList.get(i).getYear(), itemCode, "" , quantiti, price,discount,%discount);
tempListP.add(itemObj);
}
}
return itemList;
}
}
Month | Year | Sku | Detail | Quantity | Price | Discount | % Discount
7 | 2020 | 50607080 | Tshirt | 4 | 40 | 4 | 0.4
8 | 2020 | 10203040 | Tshirt | 6 | 60 | 6 | 0.6
9 | 2020 | 10203040 | Tshirt | 2 | 20 | 2 | 0.2
3 | 2021 | 10203040 | Tshirt | 3 | 30 | 3 | 0.3
8 | 2021 | 10203040 | Tshirt | 8 | 80 | 8 | 0.8
最终结果应该是:
输出:
public class Products{
private int month;
private int year;
private int sku;
private String detail;
private Double quantity;
private Double price;
private Double discount;
private Double %discount;
// getters and setters
static List<Products> sumProduct(List<Products> itemList) {
List<Product> tempListP = new ArrayList<Product>();
Collections.sort(itemList, Comparator.comparing(Product::getYear)
.thenComparing(Product::getMonth).thenComparing(Product::getSku));
Integer itemCode = null;
double quantiti = 0;
double price = 0;
double discount = 0;
double %discount = 0;
Products itemObj = null;
Integer itemMonth= null;
Integer itemYear= null;
for (int i = 0; i < itemList.size(); i++) {
if (itemCode == null || (itemCode.equals(itemList.get(i).getSku()) && itemMonth.equals(itemList.get(i).getMonth()) && itemMonth.equals(itemList.get(i).getYear()) )) {
quantiti = quantiti + itemList.get(i).getquantiti();
price = price + itemList.get(i).getprice();
discount = discount + itemList.get(i).getdiscount();
%discount = %discount + itemList.get(i).get%discount();
itemMonth = itemList.get(i).getMonth();
itemYea = itemList.get(i).getYear();
} else {
itemObj = new Product( itemList.get(i).getMonth(), itemList.get(i).getYear(), itemCode, "" , quantiti, price,discount,%discount);
if (tempListP.contains(itemObj)) {
tempListP.remove(itemObj);
}
tempListP.add(itemObj);
quantiti = 0;
quantiti = quantiti + itemList.get(i).getquantiti();
price = 0;
price = price + itemList.get(i).getprice();
discount = 0;
discount = discount + itemList.get(i).getdiscount();
%discount = 0;
%discount = %discount + itemList.get(i).get%discount();
itemMonth = itemList.get(i).getMonth();
itemYea = itemList.get(i).getYear();
}
itemCode = itemList.get(i).getSku();
if (i == itemList.size() - 1) {
itemObj = new Product( itemList.get(i).getMonth(), itemList.get(i).getYear(), itemCode, "" , quantiti, price,discount,%discount);
tempListP.add(itemObj);
}
}
return itemList;
}
}
Month | Year | Sku | Detail | Quantity | Price | Discount | % Discount
7 | 2020 | 50607080 | Tshirt | 4 | 40 | 4 | 0.4
8 | 2020 | 10203040 | Tshirt | 6 | 60 | 6 | 0.6
9 | 2020 | 10203040 | Tshirt | 2 | 20 | 2 | 0.2
3 | 2021 | 10203040 | Tshirt | 3 | 30 | 3 | 0.3
8 | 2021 | 10203040 | Tshirt | 8 | 80 | 8 | 0.8
我想创建一个函数,该函数遍历产品列表,并对具有相同月份、年份和sku的项目的值求和,然后返回数量、价格、折扣、%折扣之和的列表
但是,我如何对上述代码进行链计数和求和?特别是对于具有3个以上字段(月、年和sku)的group by。有更好的方法吗
实际上,我需要帮助对值求和,而不仅仅是对列表中的元素进行分组
提前感谢您的帮助。这个解决方案应该可以工作,我编写了一个比较器来对产品进行排序。然后,如果连续项共享相同的值,则对必要的值求和 比较器
公共类产品Comparator实现Comparator{
公共整数比较(产品p1、产品p2){
int value1=p1.年,与p2.年相比;
如果(值1==0){
int value2=p1.月,与p2.月相比;
如果(值2==0){
返回p1.sku.compareTo(p2.sku);
}否则{
返回值2;
}
}
返回值1;
}
}
求和函数
public static void main(String[] args) {
List<Products> items = new ArrayList<Products>();
items.add(new Products(8,2020,10203040,"Tshirt",1,10.00,1.00,0.1));
items.add(new Products(9,2020,10203040,"Tshirt",2,20.00,2.00,0.2));
items.add(new Products(3,2021,10203040,"Tshirt",3,30.00,3.00,0.3));
items.add(new Products(7,2020,50607080,"Tshirt",4,40.00,4.00,0.4));
items.add(new Products(8,2020,10203040,"Tshirt",5,50.00,5.00,0.5));
items.add(new Products(8,2021,10203040,"Tshirt",8,80.00,8.00,0.8));
Products.sumProduct(items);
公共静态列表产品(列表项列表){
List newList=newarraylist();
int指数=-1;
Collections.sort(itemList,newproductscomperator());
对于(产品项:itemList){
if(newList.size()!=0&&newList.get(index.getYear()==item.getYear()&&newList.get(index.getMonth()==item.getMonth()&&newList.get(index.getSku()==item.getSku()){
//增加价值
newList.get(index).setQuanti(newList.get(index).getQuanti()+item.getquantiti());
newList.get(index).setprice(newList.get(index).getprice()+item.getprice());
newList.get(index).setdiscount(newList.get(index).getdiscount()+item.getdiscount());
newList.get(索引).set%折扣(newList.get(索引).get%折扣()+商品.get%折扣());
}否则{
新建列表。添加(项);
索引++;
}
}
返回newList;
}
如果您想在一个返回值中返回这些统计信息,理想情况下,您可以使用包含这些值的结构。这是一个更好的设计,可以重用产品类来包含聚合。这是以一种会让读者感到困惑的方式重载类的使用
这是一个很好的记录用例,因为它们为您做了大量工作(例如,为您的排序和聚合定义等于和hashCode
)。您可以添加一些方便的函数来简化排序:
record MonthSKU(int month, int year, int sku) {
MonthSKU(Product product) {
this(product.month, product.year, product.sku);
}
}
record ProductStats(double quantity, double price, double discount) {
static ProductStats ZERO = new ProductStats(0, 0, 0);
ProductStats(Product product) {
this(product.quantity, product.price, product.discount);
}
ProductStats combine(ProductStats other) {
return new ProductStats(quantity + other.quantity, price + other.price, discount + other.discount);
}
}
现在,使用流运算符进行分组和求和非常简单:
Map<MonthSKU,ProductStats> stats = productList.stream()
.collect(groupingBy(MonthSKU::new,
reducing(ProductStats.ZERO, ProductStats::new, ProductStats::combine));
Map stats=productList.stream()
.收集(分组方式)(MonthSKU::新建,
减少(ProductStats.ZERO、ProductStats::new、ProductStats::combine));
在我看来,与包含聚合值的产品列表和需要排序列表的算法相比,对于输出统计而言,这是一个更容易理解的模型-这既难理解又容易打破
该模型也更易于扩展,以添加新字段或更复杂的统计数据(例如,维护计数以计算平均值)。所有这些更改都可以通过更改2条记录来实现,而分组和减少操作完全没有更改
类似地,“详细信息”字段似乎包含与sku相关的信息,而不是与产品相关的信息。如果是这样,您应该将它们放在单独的映射中或专用的sku
类中。如果不是这样,则当产品具有相同的sku但不同的详细信息时,您需要确定在汇总摘要中打印什么