java - 无限循环在程序中无法正常工作

Question

该程序使用二维数组记录开放和预订的房间。程序在开始时和每次更改数组后显示二维数组。索引值表示房间号，并针对开放房间显示。预订的房间显示预订房间的人的姓名。该程序将继续运行，直到用户输入“Q”。

除了在主方法中执行一次循环后，即使用户没有输入“Q”，程序也会停止运行，这对我来说似乎一切正常。我也试过用 while(true) 来做，但它仍然没有用。我真的希望有人能帮我解决这个问题。

public static void main (String [] args)
{
    Scanner kb = new Scanner (in);
    out.print("Enter row size: ");
    int row = kb.nextInt();
    out.print("Enter column size: ");
    int col = kb.nextInt();
    kb.nextLine();
    String [][]rooms = roomInIt(row, col);
    printMatrix(rooms);
    String a="";


    for(;;)
    {
        out.print("Would you like to reserve or release a room? Type Q to exit ");
        a = kb.nextLine();

        if (a.equalsIgnoreCase("reserve"))
        {
            out.print("How many rooms would you like to reserve? ");
            int num = kb.nextInt();
            reserveRooms(rooms, num);
        }
        else if (a.equalsIgnoreCase("release"))
        {
            out.print("How many rooms would you like to release? ");
            int x = kb.nextInt();
            releaseRooms(rooms, x);
        }
        else if (a.equalsIgnoreCase("Q"));
            break;
    }
}

public static void printMatrix(String[][]rooms)
{

    for(int r=0; r<rooms.length; r++)
        {
            for (int c=0; c<rooms[r].length; c++)
                out.print("["+r+","+c+"] "+rooms[r][c]+"\t");
            out.println();
        }
}

public static String[][] roomInIt(int row, int col)
{
    String [][]rooms = new String [row][col];
    for(int r=0; r<rooms.length; r++)
        for (int c=0; c<rooms[r].length; c++)
            rooms[r][c]="open";
    return rooms;
}

public static void reserveRooms(String [][]room, int num)
{

    Scanner kb = new Scanner(in);
    for(int i=0; i<num; i++)
    {   
        out.print("Enter name: ");
        String name = kb.nextLine();
        out.print("Enter the room number (row and column separated by a space) ");
        int r=kb.nextInt();
        int c=kb.nextInt();
        kb.nextLine();
        while (r<0 || r>room.length || c<0 || c>room[r].length || !room[r][c].equals("open"))
        {
            out.print("Invalid room number. Enter another room number (row and column separated by a space) ");
            r=kb.nextInt();
            c=kb.nextInt();
            kb.nextLine();
        }
        room[r][c] = name;
    }
    printMatrix(room);
}

public static void releaseRooms(String [][]room, int x)
{
    int r, c;
    Scanner kb = new Scanner(in);
    for(int i=0; i<x; i++)
    {   
        out.print("Enter name: ");
        String name = kb.nextLine();
        out.print("Enter the room number (row and column separated by a space) ");
        r=kb.nextInt();
        c=kb.nextInt();
        kb.nextLine();
        while(r<0 || r>room.length || c<0 || c>room[r].length)
        {
            out.print("Invalid room number. Enter another room number (row and column separated by a space) ");
            r=kb.nextInt();
            c=kb.nextInt();
            kb.nextLine();
        }
        room[r][c] = "open";

    }
    printMatrix(room);
}

Answer 1

去掉 else if (a.equalsIgnoreCase("Q")); 上的分号

; 结束语句，这意味着 break 总是完成，而不仅仅是当条件满足时。