使用哈希图更新产品购买计数

Question

我正在读取一个.txt文件，它需要能够使用产品地图中的产品密钥 5020 更新条目，从而将购买次数增加 2。到目前为止，我可以通过客户地图来做到这一点，但我也需要通过产品地图进行另一个显示。

每当我尝试以与客户映射相同的方式执行此操作时，我都不会获得文件中的所有条目。我必须使用HashMap，但我不熟悉它。

我认为问题出在产品映射的 if 语句上。

public class StoreSales {
public static void main(String[] args) {
List<Customer> customer = new ArrayList<>();
try {
readFile("Sales.txt", customer);
} catch (Exception ex) {
ex.printStackTrace();
}
System.out.println(customer);
}
public static void readFile(String file, List<Customer> cust) throws IOException, ClassNotFoundException {
Map<Integer, Customer> customers = new HashMap<>();
Map<Integer, Customer> product = new HashMap<>();
try (BufferedReader in = new BufferedReader(new FileReader(file))) {
String line;
while ((line = in.readLine()) != null) {
String[] arr = line.split(" ");
cust.add(new Customer(Integer.parseInt(arr[0]), arr[1], arr[2],
Integer.parseInt(arr[3]), arr[4], Double.parseDouble(arr[5]),
Integer.parseInt(arr[6])));
if (customers.containsKey(Integer.parseInt(arr[0]))) {
Customer c = customers.get(Integer.parseInt(arr[0]));
customers.get(Integer.parseInt(arr[0])).getSingleItemPrice();
c.addTotal(Double.parseDouble(arr[5]) * Integer.parseInt(arr[6]));
customers.put(Integer.parseInt(arr[0]), c);
} else {
customers.put(Integer.parseInt(arr[0]),
new Customer(Integer.parseInt(arr[0]), arr[1], arr[2],
Integer.parseInt(arr[3]), arr[4], Double.parseDouble(arr[5]),
Integer.parseInt(arr[6])));
}
if (product.containsKey(Integer.parseInt(arr[3]))) {
Customer p = product.get(Integer.parseInt(arr[3]));
customers.get(Integer.parseInt(arr[3])).getItemsPurchased();
p.addTotal(Double.parseDouble(arr[5]) * Integer.parseInt(arr[6]));
product.put(Integer.parseInt(arr[3]), p);
} else {
product.put(Integer.parseInt(arr[3]),
new Customer(Integer.parseInt(arr[0]), arr[1], arr[2],
Integer.parseInt(arr[3]), arr[4], Double.parseDouble(arr[5]),
Integer.parseInt(arr[6])));
}
}
}
}
}

这是文件：

1001 Martha Washington 5001 dress 120 1
1002 John Adams 5002 shirt 55 3
1002 John Adams 5003 tie 20 2
1003 George Washington 5003 tie 20 1
1004 Benjamin Franklin 5010 hat 60 1
1005 Abigail Adams 5020 blouse 45 2
1005 Abigail Adams 5013 skirt 80 1
1004 Benjamin Franklin 5015 coat 500 1
1004 Benjamin Franklin 5012 umbrella 15 1
1006 Deborah Read 5001 dress 120 2
1007 Robert Livingston 5003 tie 20 1
1002 John Adams 5010 hat 60 1
1001 Martha Washington 5014 gloves 20 1
1005 Abigail Adams 5014 gloves 20 2
1006 Deborah Read 5012 umbrella 15 4
1006 Deborah Read 5013 skirt 80 1
1004 Benjamin Franklin 5003 tie 20 5
1006 Deborah Read 5007 jacket 70 1
1001 Martha Washington 5013 skirt 80 1
1003 George Washington 5015 coat 500 1
1007 Robert Livingston 5008 pants 75 1

Answer 1

首先，你在问什么有点不清楚，代码很难阅读。所以我建议你以这种方式简化你的代码，它更容易阅读，并且会简化调试：

public static void readFile(String file, List<Customer> cust) {
Map<Integer, Customer> customers = new HashMap<>();
Map<Integer, Customer> products = new HashMap<>();
try (BufferedReader in = new BufferedReader(new FileReader(file))) {
String line;
while ((line = in.readLine()) != null) {
String[] arr = line.split(" ");
int v0 = Integer.parseInt(arr[0]);
String v1 = arr[1];
String v2 = arr[2];
int v3 = Integer.parseInt(arr[3]);
String v4 = arr[4];
double v5 = Double.parseDouble(arr[5]);
int v6 = Integer.parseInt(arr[6]);
Customer customer = new Customer(v0, v1, v2, v3, v4, v5, v6);
cust.add(customer);
if (customers.containsKey(v0)) {
Customer c = customers.get(v0);
c.getSingleItemPrice();
c.addTotal(v5 * v6);
customers.put(v0, c);
} else {
customers.put(v0, customer);
}
if (products.containsKey(v3)) {
Customer c = products.get(v3);
c.getItemsPurchased();
c.addTotal(v5 * v6);
products.put(v3, c);
} else {
products.put(v3, customer);
}
}
} catch(Exception e) {
// Handle Exception
}
}

此外，这 2 行似乎什么也没做(如果它们是合适的获取者)

c.getSingleItemPrice();

和

c.getItemsPurchased();

我看不出你在哪里增加你所说的 2。

您还可以定义用于构建客户的文件中的 7 个值是什么，并给出会产生问题的Sales.txt文件的示例。

我认为问题是：

怀疑您为同一客户提供了多种产品。

您的customers映射将customerId作为键，将Customer作为值，因此假设您具有唯一 ID，则每个客户将有一个条目。

在products映射中，您将customerId作为键，Product作为值。 如果客户有多个产品，那么您正在尝试将客户的所有产品放在同一个键上，并且它们相互替换，因此您的条目将减少。 您可能希望productsMap<Integer, List<Customer>>以便为每个产品 ID 提供一个客户列表

一个可能的解决方案：

这是相同的代码，但对产品使用Map<Integer, List<Customer>>映射

public static void readFile(String file, List<Customer> customersList) {
Map<Integer, Customer> customersByIdMap = new HashMap<>();
Map<Integer, List<Customer>> customersByProductIdMap = new HashMap<>();
try (BufferedReader in = new BufferedReader(new FileReader(file))) {
String line;
while ((line = in.readLine()) != null) {
String[] arr = line.split(" ");
// Create the Customer
int customerId = Integer.parseInt(arr[0]);
String firstName = arr[1];
String lastName = arr[2];
int productId = Integer.parseInt(arr[3]);
String productDescription = arr[4];
double singleItemPrice = Double.parseDouble(arr[5]);
int itemsPurchased = Integer.parseInt(arr[6]);
Customer customer = new Customer(customerId, firstName, lastName, productId, productDescription, singleItemPrice, itemsPurchased);
// Add it to the Customer List
customersList.add(customer);
// Add it to the customersByIdMap Map
if (customersByIdMap.containsKey(customerId)) {
Customer c = customersByIdMap.get(customerId);
c.addTotal(singleItemPrice * itemsPurchased);
customersByIdMap.put(customerId, c);
} else {
customersByIdMap.put(customerId, customer);
}
// Add it to the customersByProductIdMap Map
if (customersByProductIdMap.containsKey(productId)) {
// get the customers list for this product
List<Customer> productCustomers = customersByProductIdMap.get(productId);
// check if there is already a customer with this Id
Customer currentCustomer = null;
for(Customer c : productCustomers) {
if(c.getId() == customerId) {
currentCustomer = c;
}
}
// if yes, update it
if(currentCustomer!=null) {
currentCustomer.addTotal(singleItemPrice * itemsPurchased);
} else {
// if no, add it
productCustomers.add(customer);
customersByProductIdMap.put(productId, productCustomers);
}
} else {
List<Customer> productCustomers = new ArrayList<>();
productCustomers.add(customer);
customersByProductIdMap.put(productId, productCustomers);
}
}
} catch(Exception e) {
e.printStackTrace();
}
System.out.println("customersByIdMap: ");
System.out.println(customersByIdMap);
System.out.println("customersByProductIdMap: ");
System.out.println(customersByProductIdMap);
}

我使用了您提供的文件，它生成了以下地图

customersByIdMap:
{
1001=Customer@60e53b93, 
1002=Customer@5e2de80c, 
1003=Customer@1d44bcfa, 
1004=Customer@266474c2, 
1005=Customer@6f94fa3e, 
1006=Customer@5e481248, 
1007=Customer@66d3c617
}
customersByProductIdMap:
{
5008=[Customer@63947c6b], 
5010=[Customer@266474c2, Customer@2b193f2d], 
5012=[Customer@355da254, Customer@4dc63996], 
5013=[Customer@d716361, Customer@6ff3c5b5, Customer@3764951d], 
5014=[Customer@4b1210ee, Customer@4d7e1886], 
5015=[Customer@3cd1a2f1, Customer@2f0e140b], 
5001=[Customer@60e53b93, Customer@5e481248], 
5002=[Customer@5e2de80c], 
5003=[Customer@7440e464, Customer@1d44bcfa, Customer@66d3c617, Customer@49476842], 
5020=[Customer@6f94fa3e], 
5007=[Customer@78308db1]
}