Question

我正在学习一个部分处理打印ArrayLists元素的教程。该程序完全按照我在处理小列表时的预期运行。但是，当输入较大的数字时，字符串格式化（我相信）会导致一些奇怪的结果。

我的代码如下：

public class Theatre {
    private final String theatreName;
    public List<Seat> seats = new ArrayList<>();

    public Theatre(String theatreName, int numRows, int seatsPerRow) {
        this.theatreName = theatreName;

        int lastRow = 'A' + (numRows -1);
        for (char row = 'A'; row <= lastRow; row++) {
            for(int seatNum = 1; seatNum <= seatsPerRow; seatNum++) {
                Seat seat = new Seat(row + String.format("%02d", seatNum));
                seats.add(seat);
            }
        }
    }

    public String getTheatreName() {
        return theatreName;
    }

    public boolean reserveSeat(String seatNumber) {
        int low = 0;
        int high = seats.size()-1;

        while(low <= high) {
            System.out.print(".");
            int mid = (low + high) /2;
            Seat midVal = seats.get(mid);
            int cmp = midVal.getSeatNumber().compareTo(seatNumber);

            if(cmp <0) {
                low = mid + 1;
            } else if(cmp > 0) {
                high = mid -1;
            } else {
                return seats.get(mid).reserve();
            }
        }

            System.out.println("There is no seat " + seatNumber);
            return false;


    }

    // for testing
    public void getSeats() {
        for(Seat seat : seats) {
            System.out.println(seat.getSeatNumber());
        }
    }

    public class Seat implements Comparable<Seat > {
        private final String seatNumber;
        private boolean reserved = false;

        public Seat(String seatNumber) {
            this.seatNumber = seatNumber;
        }

        public boolean reserve() {
            if(!this.reserved) {
                this.reserved = true;
                System.out.println("Seat " + seatNumber + " reserved");
                return true;
            } else {
                return false;
            }
        }

        public boolean cancel() {
            if(this.reserved) {
                this.reserved = false;
                System.out.println("Reservation of seat " + seatNumber + " cancelled");
                return true;
            } else {
                return false;
            }
        }

        public String getSeatNumber() {
            return seatNumber;
        }

        @Override
        public int compareTo(Seat seat) {
            // returns integer greater than 0 if greater than, less than if less than, 0 if equal
            return this.seatNumber.compareTo(seat.getSeatNumber());
        }
    }

使用Main方法类：

public static void main(String[] args) {
        Theatre theatre = new Theatre("Olympian", 800, 12);
        List<Theatre.Seat> seatCopy = new ArrayList<>(theatre.seats); // shallow copy, contains references to all
                                                                        // elements of both lists, original and copy
        printList(seatCopy);


        seatCopy.get(1).reserve();
        if (theatre.reserveSeat("A02")) {
            System.out.println("Please pay for A02");
        } else {
            System.out.println("seat already reserved");
        }

        // see that they are clearly two separate array lists
        Collections.reverse(seatCopy);
        System.out.println("Printing seat copy");
        printList(seatCopy);
        System.out.println("Printing theatre.seats");
        printList(theatre.seats);
        System.out.println("Shuffling seatCopy");
        Collections.shuffle(seatCopy);
        printList(seatCopy);

    }

    public static void printList(List<Theatre.Seat> list) {
        for (Theatre.Seat seat : list) {
            System.out.print(" " + seat.getSeatNumber());
        }
        System.out.println();
        System.out.println("===============================");
    }

}

输出（我只能引用足够的内容）是：

12 ͠11 ͠10 ͠09 ͠08 ͠07 ͠06 ͠05 ͠04 ͠03 ͠02 ͠01 ͟12 ͟
===============================
Printing theatre.seats
A01 A02 A03 A04 A05 A06 A07 A08 A09 A10
===============================
===============================
 Shuffling seatCopy
V07 Ý11 11 ű05 Ú02 ̄06 ̓01 ŕ12 ȣ03 Ǔ05 S07

我知道我的字母字符用完了，而且这行格式化了：

Seat seat = new Seat(row + String.format("%02d", seatNum));

仅用于处理格式为“X ##”的席位。

我想要理解的是奇怪的字符出现的原因（“〜”和“'”等）。显然，格式化是不合适的。但为什么它会专门产生这种输出呢？

感谢您的帮助，马克

Answer 1

你自己说的。你的字母字符很少。事实上，你完全没有使用ASCII字符了。从这一行：

for (char row = 'A'; row <= lastRow; row++)

您正在做的是从“A”开始行字母并继续使用Unicode字符集。因此，超过26行，您开始获得像~这样的符号，并且有足够的行，您完全保留ASCII并开始获得类似Ý的奇怪行字母。

如果您不希望这种情况发生，您将需要放弃for循环并提出一种完全不同（且更复杂）的方式来分配行标签。

打印大型ArrayLists时出现奇数字符的原因

1 个答案: