根据用户输入从 ArrayList 中删除答案

【问题标题】：Remove from ArrayList based on user input根据用户输入从 ArrayList 中删除
【发布时间】：2021-07-27 17:46:55
【问题描述】：

为基本编程课程建立一个非常简单的车辆库存。需要添加新车辆方法、列出车辆信息方法、删除车辆方法和更新车辆属性方法。

我用 set 和 get 方法构建了一个汽车类：

    private String make;
    private String model;
    private String color;
    private int year;
    private int mileage;
    private int index;


    public Automobile(String make, String model, String color, int year,
                      int mileage, int index) {
        this.make = make;
        this.model = model;
        this.color = color;
        this.year = year;
        this.mileage = mileage;
        this.index = index;
    }



    public String getMake() {
        return make;
    }

    public void setMake(String make) {
        this.make = make;
    }

    public String getModel() {
        return model;
    }

    public void setModel(String model) {
        this.model = model;
    }

    public String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }

    public int getYear() {
        return year;
    }

    public void setYear(int year) {
        this.year = year;
    }

    public int getMileage() {
        return mileage;
    }

    public void setMileage(int mileage) {
        this.mileage = mileage;
    }

    public int getIndex() {
        return index;
    }

    public void setIndex(int index) {
        this.index = index;
    }

}

在我的 Vehicle 类中，我现在有一个看起来可以工作的 addVehicle 方法。

class Vehicle {
    static ArrayList<Automobile> vehicleList = new ArrayList<>();

    public static void addVehicle() {
        Scanner input = new Scanner(System.in);
        System.out.println("## Add Vehicle to Inventory ##");
        System.out.print("Enter Vehicle make: ");
        String make = input.nextLine();
        System.out.print("Enter Vehicle model: ");
        String model = input.nextLine();
        System.out.print("Enter Vehicle color: ");
        String color = input.nextLine();
        System.out.print("Enter Vehicle year: ");
        int year = input.nextInt();
        System.out.print("Enter Vehicle mileage: ");
        int mileage = input.nextInt();
        System.out.print("Enter the Vehicle Index Number: ");
        int index = input.nextInt();
        
        Automobile newCar = new Automobile(make, model, color, year, mileage, index);
        
        vehicleList.add(newCar);
        
        System.out.println("Vehicle Added to Inventory Successfully");

    }

但是，我坚持使用我正在尝试构建的 removeVehicle 方法：

    public void removeVehicle() {
        Scanner input = new Scanner(System.in);
        System.out.println("## Remove Vehicle from Inventory ##");
        System.out.print("Enter the Vehicle Index Number: ");
        int indexRemove = input.nextInt();

        if(    ){
            System.out.println("Vehicle Removed Successfully");
        }
        else{
            System.out.println("No Such Vehicle Exists");
        }

    }

我认为删除车辆的最简单方法是要求用户输入车辆索引号，然后从数组中删除该特定索引号。但我似乎无法取得任何进展，也无法理解从这里去哪里。

【问题讨论】：

标签： java arraylist

【解决方案1】：

给你！如果您曾经调用过您的删除车辆方法，我还会显示您列表中的所有车辆。

解决方案 1

我几乎创建了一个 foreach 循环，它遍历您现有的列表并通过提供的索引检查是否存在。然后它在 if 语句中将其删除。如果成功删除，则为真，否则为假。

   public void removeVehicle() {
        Scanner input = new Scanner(System.in);
        System.out.println("## Remove Vehicle from Inventory ##");
        
        for(Automobile vehicle : vehicleList){
            System.out.println("make: " + vehicle.make  + "-" + "model: " + vehicle.model + "-" + 
                    "color: " + vehicle.color + "-" + "year: " +  vehicle.year + "-" + 
                    "mileage: " + vehicle.mileage + "-" + "index: " + vehicle.index);
        }
        
        System.out.print("Enter the Vehicle Index Number: ");
        int indexRemove = input.nextInt();
        
        Automobile automobileToBeRemoved = null;
        for(Automobile vehicle : vehicleList){
            if(vehicle.index == indexRemove){
                automobileToBeRemoved = vehicle;
                break;
            }
        }
        
        if(vehicleList.remove(automobileToBeRemoved)){
            System.out.println("Vehicle Removed Successfully");
        }
        else{
            System.out.println("No Such Vehicle Exists");
        }

    }

解决方案 2

      public void removeVehicle() {
        Scanner input = new Scanner(System.in);
        System.out.println("## Remove Vehicle from Inventory ##");

        System.out.print("Enter the Vehicle Index Number: ");
        int indexRemove = input.nextInt();

        boolean removed = false;
        for (Automobile vehicle : vehicleList) {
            if (vehicle.index == indexRemove) {
                removed = vehicleList.remove(vehicle);
                break;
            }
        }

        if (removed) {
            System.out.println("Vehicle Removed Successfully");
        } else {
            System.out.println("No Such Vehicle Exists");
        }

解决方案 3

        public void removeVehicle() {
        Scanner input = new Scanner(System.in);
        System.out.println("## Remove Vehicle from Inventory ##");

        System.out.print("Enter the Vehicle Index Number: ");
        int indexRemove = input.nextInt();

        int originalSize = vehicleList.size();
        vehicleList = vehicleList.stream().filter(vehicle -> vehicle.index != indexRemove)
                .collect(Collectors.toCollection(ArrayList::new));

        if (vehicleList.size() != originalSize) {
            System.out.println("Vehicle Removed Successfully");
        } else {
            System.out.println("No Such Vehicle Exists");
        }
    }

解决方案 4

        public void removeVehicle() {
        Scanner input = new Scanner(System.in);
        System.out.println("## Remove Vehicle from Inventory ##");

        System.out.print("Enter the Vehicle Index Number: ");
        try{
            int indexRemove = input.nextInt();
            int originalSize = vehicleList.size();
            vehicleList = vehicleList.stream().filter(vehicle -> vehicle.index != indexRemove)
                    .collect(Collectors.toCollection(ArrayList::new));

            if (vehicleList.size() != originalSize) {
                System.out.println("Vehicle Removed Successfully");
            } else {
                System.out.println("No Such Vehicle Exists");
            }
        } catch (Exception e){
                System.out.println("No Such Vehicle Exists");
        }
    }

MISC 导出：

        public void writeFile() {
        try {
            FileWriter fw = new FileWriter("output.txt");
            for (Automobile vehicle : vehicleList) {
                fw.write("make: " + vehicle.make + "-" + "model: " + vehicle.model + "-" +
                        "color: " + vehicle.color + "-" + "year: " + vehicle.year + "-" +
                        "mileage: " + vehicle.mileage + "-" + "index: " + vehicle.index + "\n");
            }
            fw.close();
            System.out.println("File exported.");
        } catch (IOException e) {
            System.out.println("Error writing file.");
        }
    }

【讨论】：

非常感谢。感谢您花时间提供多种解决方案。我可以在解决方案 2 的 if/else 语句中轻松实现 try/catch 吗？
我能看到你实现 try/catch 的唯一地方是“int indexRemove = input.nextInt();”如果有人给你一个字符串而不是一个数字。我将其添加为解决方案 4。
有趣。但实际上，使用我的 removeVehicle 方法，如果输入的不是适用的索引号，那么它会给出“不存在这样的车辆”，对吗？我需要在某个地方尝试/捕获，所以我正在考虑将它包含在我必须构建的 printFile() 方法中。它需要显示一条消息，询问用户是否要将信息打印到文件（是或否），然后将文件打印到预定义的位置（例如，C:\Temp\Autos.txt）。我还不是 100% 确定那会是什么样子，但感觉就像是正确的道路。想法？
如果需要，您可以在打印文件上执行此操作，但我刚刚更新了解决方案 4，如果他们在 int 之外输入任何内容，则显示“不存在此类车辆”。
我可以完全理解解决方案 2，它是目前对我来说最有意义的一个。从知识的角度来看，增强 for 循环的简单性与我所处的位置有关。您建议从哪里开始打印文件？您的解决方案 3 会打印整个库存，但将其写入文件则是另一回事。

【解决方案2】：

public void removeVehicle() {
    Scanner input = new Scanner(System.in);
    System.out.println("## Remove Vehicle from Inventory ##");
    System.out.print("Enter the Vehicle Index Number: ");
    int indexRemove = input.nextInt();

    int oldSize = vehicleList.size();

    for (Automobile vehicle : vehicleList) {
        if (auto.getIndex() == indexRemove) {
            vehicleList.remove(vehicle);
            System.out.println("Vehicle Removed Successfully");
            break;
        }
    }

    if (vehicleList.size() == oldSize) {
        System.out.println("No Such Vehicle Exists");
    }
}

【讨论】：

【解决方案3】：

尝试使用 listIterator，因为它可以帮助您遍历列表，也可以帮助您从列表中删除元素

public static void removeVehicle() {
    Scanner input = new Scanner(System.in);
    System.out.println("## Remove Vehicle from Inventory ##");
    System.out.print("Enter the Vehicle Index Number: ");        
    int indexRemove = input.nextInt();
    ListIterator<Automobile> listIterator = vehicleList.listIterator();
    boolean removed = false;
    while(listIterator.hasNext()) {
        if(listIterator.next().getIndex()==indexRemove) {
            listIterator.remove();
            removed = true;
            break;
        }
    }
    if(removed) {
        System.out.println("Vehicle Removed Successfully");
    }
    else {
        System.out.println("No Such Vehicle Exists");
    }
}

【讨论】：

我一直在尝试将 ListIterator 用于库存的“更新车辆”部分。我需要它来更新车辆，打印返回值，然后调用列表方法并将信息打印到屏幕上。我想我很接近，但对这个功能很不熟悉。
public static <AutoMobile> void updateVehicle() { Scanner input = new Scanner(System.in); System.out.println("## Remove Vehicle from Inventory ##"); System.out.print("Enter the make of Automobile: "); String make = input.nextLine(); System.out.print("Enter the model of Automobile: "); String model = input.nextLine(); System.out.print("Enter the Vehicle Index Number: "); ListIterator<AutoMobile> iterator =(ListIterator<AutoMobile>) vehicleList.listIterator(); while(iterator.hasNext()){

【解决方案4】：

从 Java 8 开始，Collection（因此是List）具有方法removeIf (Predicate p)，它允许删除满足应用于集合的每个元素的给定谓词的所有元素，因此方法并返回true（如果有）元素已被删除：

public void removeVehicle() {
    Scanner input = new Scanner(System.in);
    System.out.println("## Remove Vehicle from Inventory ##");
    System.out.print("Enter the Vehicle Index Number: ");
    int indexRemove = input.nextInt();

    if (vehicleList.removeIf(car -> indexRemove == car.getIndex())) {
        System.out.println("Vehicle Removed Successfully");
    } else {
        System.out.println("No Such Vehicle Exists");
    }
}

【讨论】：

【解决方案5】：

根据您对 updateVehicle 方法的要求，您可以使用以下代码，但是有了这个，我建议你重写 toString() 方法，如果你重写 hashcode 和 equals 方法会更好

public static void updateVehicle() {
    Scanner input = new Scanner(System.in);
    System.out.println("## Upadate Vehicle by index number ##");
    System.out.print("Enter the Vehicle Index Number: ");        
    int indexRemove = input.nextInt();
    ListIterator<Automobile> listIterator = vehicleList.listIterator();
    boolean updated = false;
    while(listIterator.hasNext()) {
        Automobile mobile = listIterator.next(); 
        if(mobile.getIndex()==indexRemove) {
            
            System.out.println("Existing details : "+mobile.toString());
            
            System.out.print("Enter Vehicle make: ");
            String make = input.nextLine();
            System.out.print("Enter Vehicle model: ");
            String model = input.nextLine();
            System.out.print("Enter Vehicle color: ");
            String color = input.nextLine();
            System.out.print("Enter Vehicle year: ");
            int year = input.nextInt();
            System.out.print("Enter Vehicle mileage: ");
            int mileage = input.nextInt();
            
            mobile.setMake(make);
            mobile.setModel(model);
            mobile.setModel(model);
            mobile.setColor(color);
            mobile.setYear(year);
            mobile.setMileage(mileage);
            
            
            updated = true;
            break;
        }
    }
    if(updated) {
        System.out.println("Vehicle Updated Successfully");
    }
    else {
        System.out.println("No Such Vehicle Exists");
    }
}

【讨论】：