如何更新数组列表中的用户输入？

Question

所以我正在为汽车经销商制作一个程序，作为我班级的最后一个项目。此时我会说我完成了大约 75%，但我无法弄清楚如何更新用户在数组列表中的输入。所以每个数组列表槽都包含汽车的年份、品牌、型号、颜色和里程数。我可以添加一辆新车，我可以移除一辆汽车，我可以退出我的程序。我尝试了很多东西，我阅读了很多论文、博客、论坛和我的课本，但它总是随着程序员的输入而更新。

package carDealer;

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

public class VehicleInformation {

public static void main(String [] args) {

    Scanner scnr = new Scanner(System.in);
    ArrayList<VehicleInventory> car = new ArrayList<VehicleInventory>();
    String userInput = "-";

    while (!userInput.equals("q")) {
        System.out.println("Commands: 'a' to add, 'd' to delete, 'e' to edit, 'q' to quit");
        userInput = scnr.next();

        if (userInput.equals("a")) {
            System.out.println("Year: ");
            int year = scnr.nextInt();
            System.out.println("Make: ");
            String make = scnr.next();
            System.out.println("Model: ");
            String model = scnr.next();
            System.out.println("Color: ");
            String color = scnr.next();
            System.out.println("Mileage: ");
            int mileage = scnr.nextInt();

            VehicleInventory userCar = new VehicleInventory();      
            userCar.setMake(make);
            userCar.setModel(model);
            userCar.setYear(year);
            userCar.setColor(color);
            userCar.setMileage(mileage);
            userCar.print();

            addCar(car, userCar);
        }

        if (userInput.equals("d")) {
            for (int i = 0; i < car.size(); ++i) {
                System.out.print((i + 1) + " ");
                car.get(i).print();
            }

            System.out.println("List number: ");
            int userNum = scnr.nextInt();
            car.remove(userNum - 1);
            System.out.println("count: " + car.size());
        }

        if (userInput.equals("e")) {
            for (int i = 0; i < car.size(); ++i) {
                System.out.print((i + 1) + " ");
                car.get(i).print();

            }

            System.out.println("List number: ");
            int userNum = scnr.nextInt();
            car.get(userNum - 1);

Answer 1

您可以执行一个循环来查找用户想要更新的汽车模型（它可以是任何其他属性），一旦找到，将其值更新为所需的值：

String vehicleToLookUp = "golf"; // This will be received by user input
String vehicleNewName = "golf gti"; // This will be received by user input
for( int i = 0; i < car.size(); i++){
    if(vehicleToLookUp.getModel().equals(car.get(i)){
        car.get(i).setSomeAttribute(...); // Set the desired attribute here
    }
}

或者如果你想替换整个对象...

String vehicleToLookUp = "golf"; // This will be received by user input
VehicleInventory newVehicle = new VehicleInventory(); // You will set the attributes by user input
for( int i = 0; i < car.size(); i++){
    if(vehicleToLookUp.getModel().equals(car.get(i)){
        car.set(i, newVehicle ); // Create your object and pass it here
    }
}

此外，您可以使用if/else if 甚至switch/case 而不是所有那些if，以获得更好的性能/可读性（认为即使您的逻辑对于第一个if 是正确的，它也会检查所有你创建的另一个if，浪费时间和处理能力。