我如何在java中增加静态变量

Question

我对 java 很陌生，但我对 c++ 和 python 有很好的经验。所以，我正在做一个问题，我需要实施一个飞机预订系统，它执行以下操作 -

1.将所有座位初始化为未占用(false)

2.询问输入（生态或头等舱）

3.检查座位是否未被占用

4.如果座位没有被占用分配座位，否则寻找下一个座位

5.如果经济舱已订满，询问用户是否想升到头等舱

6.如果用户是否定的显示消息“下一个飞机在 3 小时内”

但是，

package oop;
import java.util.Arrays;
import java.util.Scanner;

public class AirplaneBooking {

    private final static int MAX_ECO_SEATS = 5;
    private final static int MAX_FIRST_CLASS_SEATS = 3;
    private final static boolean[] ECO_SEATS = new boolean[MAX_ECO_SEATS];
    private final static boolean[] FIRST_CLASS_SEATS = new boolean[MAX_FIRST_CLASS_SEATS];
    private static int current_eco_seat = 0;
    private static int current_first_class_seat = 0;

    public static void initialilze_seats(boolean[] first_class_seats, boolean[] eco_class_seats){
        Arrays.fill(first_class_seats, Boolean.FALSE);
        Arrays.fill(eco_class_seats, Boolean.FALSE);
    }

    public static void display(boolean[] seats){
        System.out.print("[");
        for(boolean seat : seats){
            System.out.print(seat + ",");
        }
        System.out.println("]");
    }

    public static void book_seat(boolean [] seats, int current_seat){
        seats[current_seat] = true;
        current_seat++;
        System.out.println(current_seat);
    }


    public static int user_input() {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter 1 for Economy class or 2 for First class : ");
        int user_seat_prefrence = input.nextInt();
        if (user_seat_prefrence == 1){
            if(current_eco_seat < MAX_ECO_SEATS){
                book_seat(ECO_SEATS, current_eco_seat);
            }
            else{
                System.out.println("Looks like eco seats are full, would you like to book for first class insted(1/0) ?");
                Scanner next_input = new Scanner(System.in);
                int user_next_seat_prefrence = next_input.nextInt();
                if (user_next_seat_prefrence == 1){
                    book_seat(FIRST_CLASS_SEATS, current_first_class_seat);
                    user_seat_prefrence = 2;
                }
                else{
                    System.out.println("next flight leaves in 3 hrs");
                }
            }

        }

        else if  (user_seat_prefrence == 2){
            if (current_first_class_seat < MAX_FIRST_CLASS_SEATS){
                book_seat(FIRST_CLASS_SEATS, current_first_class_seat);
            }
            else{
                System.out.println("Looks like first class seats are full, would you like to book economy instead?(1/0)");
                int user_next_seat_prefrence = input.nextInt();
                if (user_next_seat_prefrence == 1){
                    book_seat(ECO_SEATS, current_eco_seat);
                    user_seat_prefrence = 1;
                }
                else{
                    System.out.println("Next flight leaves in 3hrs");
                }

            }
        }

        else {
            System.out.println("Enter valid option");
        }

        return user_seat_prefrence;
    }

    public static void print_boarding_pass(int user_seat_prefrence){
        if (user_seat_prefrence == 1){
            System.out.println("eco");
            System.out.println(current_eco_seat - 1);
        }
        else{
            System.out.println("first class");
            System.out.println(current_first_class_seat - 1); 
        }
    }
    public static void main(String args[]){
        initialilze_seats(FIRST_CLASS_SEATS, ECO_SEATS);
        display(FIRST_CLASS_SEATS);
        display(ECO_SEATS);
        while(true){
            int user_seat_prefrence = user_input();
            print_boarding_pass(user_seat_prefrence);    
            display(FIRST_CLASS_SEATS);
            display(ECO_SEATS);
            System.out.print("book another seat:");
            Scanner choice = new Scanner(System.in);
            boolean book_another_seat = choice.nextBoolean();
            if (book_another_seat == false)
                break;
         
        }
    }

}

我遇到此代码的问题是如果生态舱的座位（例如）已满，程序应该询问我是否要预订头等舱并等待我的输入，如果我按下1 它应该在头等舱预订，但程序不会等待我的输入，而是转到 else 语句。

另外，我使用static 变量current_eco_seat 和current_first_class_seat 来跟踪当前预订的座位，并将该静态变量传递给book_seat 函数，然后程序预订座位并递增current_eco_seat 或 current_first_class_seat（取决于通过的）以便可以在下一次互动中预订下一个座位。但是静态变量根本不会增加。

这些是我对程序唯一的问题。

感谢任何帮助，谢谢

Answer 1

由于 Java 按值调用方法，

您关于静态的问题是您将current_seat 的值传递给book_seat 方法，因此从该方法返回后更改该值不会影响该变量。

要解决它，只需调用该方法，不要传递您的静态变量。它是静态的，因此您可以从任何地方访问它。

即：

public static void book_seat(boolean [] seats){
        seats[current_seat] = true;
        current_first_class_seat++;
        System.out.println(current_seat);
    }

Answer 2

您不需要坚持增加确切的变量，只需执行以下操作：

1. 使book_seat() 返回递增值

    public static int book_seat(boolean [] seats, int current_seat) {
        seats[current_seat] = true;
        System.out.println(current_seat + 1);
        return current_seat + 1;
    }

1. 将返回值设置为current_first_class_seat 或current_eco_seat

            if (current_first_class_seat < MAX_FIRST_CLASS_SEATS){
                current_first_class_seat = book_seat(FIRST_CLASS_SEATS, current_first_class_seat);
            }
            else{
                System.out.println("Looks like first class seats are full, would you like to book economy instead?(1/0)");
                int user_next_seat_prefrence = input.nextInt();
                if (user_next_seat_prefrence == 1){
                    current_eco_seat = book_seat(ECO_SEATS, current_eco_seat);
                    user_seat_prefrence = 1;
                }
                else{
                    System.out.println("Next flight leaves in 3hrs");
                }

            }

然后您可以使用book_seat() 来处理您之前计划的经济舱和头等舱预订。

Answer 3

1. 检查 Inout 流

不确定您的问题是与“静态”变量有关，还是与“如何处理输入流？”有关。

关于：

如果我按 1，它应该在头等舱预订，但程序不会等待我的输入，而是继续执行 else 语句。

在再次阅读之前，您应该考虑“刷新”输入流。 flush-clear-system-in-stdin-before-reading

1. 方法参数用法

另一方面，这种方法是错误的

    public static void book_seat(boolean [] seats, int current_seat){
    seats[current_seat] = true;
    current_seat++;
    System.out.println(current_seat);
}

此命令没有任何影响，但会向用户打印信息。您在调用者“current_eco_seat”中使用的变量根本不会改变。