Java中基于ArrayList存储数组模拟数据库的账户管理实现问询

Hey Luis, let's tackle your questions one by one and get your customer management program working smoothly! First, let's fix the repetitive input code with a for loop, then add the ID-based operations you need.

1. 用For循环简化客户信息填充 #

Your original code manually assigns values to each index of newCustomer, which creates a lot of repetitive code. We can define an array of field names first, then use a for loop to iterate through this array, prompt the user for input in sequence, and automatically fill the newCustomer array. This is not only concise but also easier to maintain:

import java.util.ArrayList;
import java.util.Scanner;

public class CustomersDB {
    private static Scanner scanner = new Scanner(System.in);
    private ArrayList<String[]> custList = new ArrayList<>();

    // Define customer information field names, corresponding to array indices
    private static final String[] CUST_FIELDS = {
        "Name", "Surname", "ID", "Phone", "Email", "Address", "City", "State", "Zip Code"
    };

    public void createCustomer() {
        String[] newCustomer = new String[9]; // Each customer has 9 fields

        // Use for loop to iterate through fields and fill the array
        for (int i = 0; i < CUST_FIELDS.length; i++) {
            System.out.println(CUST_FIELDS[i] + ": ");
            newCustomer[i] = scanner.nextLine().trim(); // Trim whitespace from input

            // Call corresponding set methods (if needed)
            switch(i) {
                case 0: setCustName(newCustomer[i]); break;
                case 1: setCustSurname(newCustomer[i]); break;
                case 2: setCustID(newCustomer[i]); break; // Fixed wrong method name in your original code
                // Add other field set methods here
            }
        }

        custList.add(newCustomer);
        System.out.println("Customer created successfully!");
    }

    // Example set methods (you can refine these with validation logic)
    private void setCustName(String name) {
        if (name.isEmpty()) {
            System.out.println("Warning: Name cannot be empty!");
        }
    }

    private void setCustSurname(String surname) {
        // Add validation logic here if needed
    }

    private void setCustID(String id) {
        // Check for duplicate IDs to avoid conflicts
        if (findCustomerById(id) != null) {
            System.out.println("Warning: This ID already exists!");
        }
    }
}

2. ID-Based Query, Delete, and Edit Operations #

The core idea is to iterate through custList and find the customer array matching the target ID (since your ID is stored at index 2 of the String[]). Here are the specific implementations:

2.1 Query Customer by ID #

// Find customer by ID, return the corresponding String[], or null if not found
public String[] findCustomerById(String targetId) {
    for (String[] customer : custList) {
        // Avoid NullPointerException by checking for null first
        if (customer != null && targetId.equals(customer[2])) {
            return customer;
        }
    }
    return null;
}

// Display query results
public void displayCustomer(String id) {
    String[] customer = findCustomerById(id);
    if (customer != null) {
        System.out.println("===== Customer Details =====");
        for (int i = 0; i < CUST_FIELDS.length; i++) {
            System.out.println(CUST_FIELDS[i] + ": " + customer[i]);
        }
    } else {
        System.out.println("Customer with ID " + id + " not found!");
    }
}

2.2 Delete Customer by ID #

public boolean deleteCustomer(String targetId) {
    // Use iterator to avoid exceptions when modifying the collection during iteration
    for (var iterator = custList.iterator(); iterator.hasNext();) {
        String[] customer = iterator.next();
        if (targetId.equals(customer[2])) {
            iterator.remove();
            System.out.println("Customer deleted successfully!");
            return true;
        }
    }
    System.out.println("Customer with ID " + targetId + " not found!");
    return false;
}

2.3 Edit Customer Information by ID #

public boolean editCustomer(String targetId) {
    String[] customer = findCustomerById(targetId);
    if (customer == null) {
        System.out.println("Customer not found!");
        return false;
    }

    System.out.println("Which field do you want to edit?");
    // Print all field options
    for (int i = 0; i < CUST_FIELDS.length; i++) {
        System.out.println((i+1) + ". " + CUST_FIELDS[i]);
    }
    int choice = scanner.nextInt();
    scanner.nextLine(); // Consume the newline character left by nextInt()

    if (choice < 1 || choice > CUST_FIELDS.length) {
        System.out.println("Invalid choice!");
        return false;
    }

    int fieldIndex = choice - 1;
    System.out.println("Enter new " + CUST_FIELDS[fieldIndex] + ": ");
    String newValue = scanner.nextLine().trim();
    customer[fieldIndex] = newValue;

    // Call corresponding set methods for validation
    switch(fieldIndex) {
        case 0: setCustName(newValue); break;
        case 1: setCustSurname(newValue); break;
        case 2: 
            // Check for duplicate ID when editing
            if (findCustomerById(newValue) != null) {
                System.out.println("Warning: This ID already exists! Reverting change.");
                customer[fieldIndex] = targetId; // Revert to original ID
                return false;
            }
            setCustID(newValue);
            break;
    }

    System.out.println("Customer updated successfully!");
    return true;
}

3. Extra Suggestions #

• Use a Class Instead of String Array: While you're using a String array to store customer info now, a more standard approach is to create a Customer class with attributes like name, surname, id, etc. This makes the code much more readable and maintainable. For example:

  class Customer {
      private String name;
      private String surname;
      private String id;
      // Add other attributes, getters, and setters here
  }
  

  Then use ArrayList<Customer> to store data, which makes operations more intuitive.
• Input Validation: Add necessary validation when getting user input (e.g., non-empty ID/name, unique ID) to avoid storing invalid data.
• Menu System: Add a main menu to let users choose between create, query, delete, and edit operations for better interactivity.

内容的提问来源于stack exchange，提问作者Luis Fernandes