如何在Java中递增静态变量。

huangapple go评论79阅读模式
英文:

How do i increment static variables in java

问题

以下是您提供的代码的翻译部分:

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 instead(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");
                }
            }
        }
        // ... 其余部分类似,未翻译

        return user_seat_prefrence;
    }

    // ... 其余部分类似,未翻译

    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;
        }
    }
}

请注意,代码中可能仍存在错误或需要进一步调试。如果您有其他问题或需要进一步的解释,请随时提问。

英文:

I'm very new to java but i have decent experience with c++ and python. So, I'm doing a question in which im required to implement an airplane booking system, which does the following -

1.initialize all seats to not occupied(false)

2.ask for input(eco or first class)

3.check if seat is not occupied

4.if seat is not occupied allocate seat else look for next seat

5.if economy seats are booked out, ask if user wants to bump up to first class

6.if user is negative display msg "next plane is in 3hrs"

but,

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(&quot;[&quot;);
for(boolean seat : seats){
System.out.print(seat + &quot;,&quot;);
}
System.out.println(&quot;]&quot;);
}
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(&quot;Enter 1 for Economy class or 2 for First class : &quot;);
int user_seat_prefrence = input.nextInt();
if (user_seat_prefrence == 1){
if(current_eco_seat &lt; MAX_ECO_SEATS){
book_seat(ECO_SEATS, current_eco_seat);
}
else{
System.out.println(&quot;Looks like eco seats are full, would you like to book for first class insted(1/0) ?&quot;);
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(&quot;next flight leaves in 3 hrs&quot;);
}
}
}
else if  (user_seat_prefrence == 2){
if (current_first_class_seat &lt; MAX_FIRST_CLASS_SEATS){
book_seat(FIRST_CLASS_SEATS, current_first_class_seat);
}
else{
System.out.println(&quot;Looks like first class seats are full, would you like to book economy instead?(1/0)&quot;);
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(&quot;Next flight leaves in 3hrs&quot;);
}
}
}
else {
System.out.println(&quot;Enter valid option&quot;);
}
return user_seat_prefrence;
}
public static void print_boarding_pass(int user_seat_prefrence){
if (user_seat_prefrence == 1){
System.out.println(&quot;eco&quot;);
System.out.println(current_eco_seat - 1);
}
else{
System.out.println(&quot;first class&quot;);
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(&quot;book another seat:&quot;);
Scanner choice = new Scanner(System.in);
boolean book_another_seat = choice.nextBoolean();
if (book_another_seat == false)
break;
}
}
}

The problem i'm having with this code is if the seats for eco class(for example) are full, the program is supposed to ask if i want to book for first class instead and wait for my input, if I press 1 it should book in first class but the program does not await for my input and proceeds to else statement instead.

Also, i use a static variable current_eco_seat and current_first_class_seat to keep track of the current seat being booked, and i pass that static variable to book_seat function, the program then books the seat and increments the current_eco_seat or current_first_class_seat(depending which is passed) so that next seat can be booked in next interation. But the static variable does not get incremented at all.

These are the only problems i have with the program.

Any help is appreciated, thanks

答案1

得分: 1

由于Java是按值调用方法,

关于静态变量的问题是,你将current_seat的值传递给了book_seat方法,所以在从方法返回后更改该值不会影响该变量。

要解决这个问题,只需调用方法而不传递静态变量。它是静态的,因此你可以在任何地方访问它。

例如:

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

As Java calls methods by value,

Your problem about static is you are passing the value of current_seat to the book_seat method, so changing the value doesn't affect that variable after returning from the method.

To solve it just call the method and do not pass your static vars. It's static, so you have access it from everywhere.

i.e:

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

答案2

得分: 0

  1. 检查输入流

不确定你的问题是与“静态”变量有关还是更与“如何处理输入流?”有关。

关于:

> 如果我按1,它应该预订头等舱,但程序不等待我的输入,而是继续执行else语句。

你应该考虑在再次读取之前“刷新”输入流。清除输入流中的数据以便读取

  1. 方法参数的使用

另一方面,这个方法是错误的

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

这个命令没有影响,只是向用户输出信息。你在调用者中使用的变量“current_eco_seat”根本不会改变。

英文:
  1. Checking Inout stream

Not sure wether your question is related to "static" variables or more related to "How to handle Input Stream?".

Regarding:

> if I press 1 it should book in first class but the program does not await for my input and proceeds to else statement instead.

You should think about "flushing" the Input Stream before reading again. flush-clear-system-in-stdin-before-reading

  1. Method Parameter usage

On the other hand this method is wrong

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

this command has no affect, but printing an information to the User. The variable you used in the caller "current_eco_seat" will not change at all.

答案3

得分: 0

你不需要坚持递增确切的变量,只需执行以下操作:

  1. 使 book_seat() 返回递增的值
    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. 将返回的值设置为 current_first_class_seatcurrent_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,您可以像之前预期的那样,对经济舱和头等舱的预订处理都使用 book_seat()

英文:

you don't need to insist incrementing the exact variable, just do the following :

  1. make book_seat() to return incremented value
    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. set returned value to current_first_class_seat or current_eco_seat
            if (current_first_class_seat &lt; MAX_FIRST_CLASS_SEATS){
                current_first_class_seat = book_seat(FIRST_CLASS_SEATS, current_first_class_seat);
            }
            else{
                System.out.println(&quot;Looks like first class seats are full, would you like to book economy instead?(1/0)&quot;);
                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(&quot;Next flight leaves in 3hrs&quot;);
                }

            }

Then you can use book_seat() for both eco and first class reservations handling as previously you have intended.

huangapple
  • 本文由 发表于 2020年10月26日 15:19:38
  • 转载请务必保留本文链接:https://go.coder-hub.com/64532869.html
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