代码在 Java（数组）中不起作用

Question

I have an assignment to write a code that ask you for 10 seats (some are taken and some are empty) and you need to get a seat, check if it is available and if not find the closest seat that is empty.

Some times my code works, but most of the time it doesn't. Can someone help me?

import java.util.Scanner;

public class Main {
    static Scanner reader = new Scanner(System. in );

    public static void main(String[] args) {
        int mult = 1;
        int[] manage = new int[10];
        System.out.println(" 0- empty   1-taken ");
        for (int i = 0; i < 10; i++) {
            System.out.println("enter the " + (i + 1) + " place");
            manage[i] = reader.nextInt();
        }
        int a = 0, check = 0;
        System.out.println("What the place you want to seat in?: ");
        a = (reader.nextInt()) + 1;
        System.out.println("checking...");
        while (check != 5) {
            if (manage[a] == 0) {
                System.out.println(" your seat is in the " + a + " place");
                check = 5;
            } else if (manage[a - mult] == 0) {
                System.out.println(" your seat is in the " + ((a - mult) + 1) + " place");
                check = 5;
            } else if (manage[a + mult] == 0) {
                System.out.println(" your seat is in the " + ((a + mult) + 1) + " place");
                check = 5;
            } else {
                mult++;
            }
        }
    }
}   

Answer 1

I think what you want for this line is

a = (reader.nextInt()) - 1;

instead of

a = (reader.nextInt()) + 1;

Since you are always displaying the 'actual index + 1' for all your outputs, ie
The user deals with 1 - 10 and not 0 - 9 ?

Note: manage[a - mult] and manage[a + mult] can throw ArrayIndexOutOfBoundsException if the value is < 0 or the value is >= array length .

Note #2: In the else clause, once mult is >= array length, you can break out of the loop. If you do not add that in, the loop will keep repeating if all the seats are taken right from the start.

So, add a check before accessing that array index, as shown here:

if (manage[a] == 0) {
    System.out.println("Your seat is in the " + a + " place");
    check = 5;
} else if ( a - mult >= 0 && manage[a - mult] == 0) {
    System.out.println("Your seat is in the " + ((a - mult) + 1)
            + " place");
    check = 5;
} else if (a + mult < manage.length && manage[a + mult] == 0) {
    System.out.println("Your seat is in the " + ((a + mult) + 1)
            + " place");
    check = 5;
} else {
    mult++;
    // Check is necessary here, infinite loop if all seats are taken!
    if(mult >= manage.length) {
        System.out.println("All seats taken!");
        break;
    }
}

Input/Output (after making the change):

0 - Empty  1 - Taken 
Enter the 1 place: 0
Enter the 2 place: 0
Enter the 3 place: 1
Enter the 4 place: 1
Enter the 5 place: 1
Enter the 6 place: 1
Enter the 7 place: 1
Enter the 8 place: 1
Enter the 9 place: 1
Enter the 10 place: 1
What is the place you want to sit in?: 10
checking...
Your seat is in the 2 place

0 - Empty  1 - Taken 
Enter the 1 place: 1
Enter the 2 place: 1
Enter the 3 place: 1
Enter the 4 place: 1
Enter the 5 place: 0
Enter the 6 place: 1
Enter the 7 place: 1
Enter the 8 place: 1
Enter the 9 place: 0
Enter the 10 place: 1
What is the place you want to sit in?: 1
checking...
Your seat is in the 5 place

In the above example, user enters 10, but your program checks for array index 9.
Array index 9 is taken, so you check array index 8 (9-1), which is empty, and tells the user that seat #9 is his seat.