Java数组-初始化的数组超出范围的异常

Question

I'm getting an out of bounds exception on the "calendarTable[i][j] = str;" line below. I find this funny because I'm initializing it to 15, and I only iterate to 14. I've tried initializing to 20000 and no matter how large of an array I make, it still gets an index out of bounds error.

public static void main(String[] args) {
        Calendar cal = new GregorianCalendar();
        cal.set(2012, 2, 1);
        cal.set(Calendar.DAY_OF_WEEK, 1);
        int dayOfMonth = 1;
        Object[][] calendarTable = new Object[15][15];
        calendarTable[0] = new String[]{"SUNDAY", "MONDAY", "TUESDAY", "WEDNESDAY", "THURSDAY", "FRIDAY", "SATURDAY"};
        for (int i = 0; i < 14; i++) {
            for (int j = 0; j < 14; j++) {
                //calendarTable[i][j] = dayOfMonth++;
                if(i%2 == 0){
                    String str = String.valueOf(cal.get(Calendar.DAY_OF_MONTH));
                    calendarTable[i][j] = str;
                    cal.add(Calendar.DAY_OF_YEAR, 1);
                }else{
                    calendarTable[i][j] = dayOfMonth;
                }
                calendarTable[i * 2 + 1][j] = "TEST";
            }
        }
        for (int i = 0; i < 14; i++) {
            for (int j = 0; j < 14; j++) {
                System.out.print(calendarTable[i][j]);
            }
            System.out.println("");
        }
    }

Answer 1

You have initialized it to 15*15 , but then promptly replaced the initial entry with a seven-item array. By the time you get into the iteration, the array at the element zero has only seven items, not fifteen. If you would like to keep it 15*15 , copy the names of the days into the array of 15 items.

System.arrayCopy(
    new String[]{"SUNDAY", "MONDAY", "TUESDAY", "WEDNESDAY", "THURSDAY", "FRIDAY", "SATURDAY"}
,   0
,   calendarTable[0]
,   0
,   7);

Also if you would like the index to go full length of the array, use i != 15 , i < 15 , or i <= 14 .

Answer 2

Because you're running your loop until index < 14

However you have only 7 days in 2nd dimension.

FIX: If you change all occurrences of 14 to 7 then this exception will be fixed however you will have still make sure whether your required output is coming or not.

Answer 3

Because CalendarTable only has 6 indices and it dies when it goes above that value.

if (i % 2 == 0)
        {
            String str = String.valueOf(cal.get(Calendar.DAY_OF_MONTH));
            System.out.println("current value of j: " + j);
            calendarTable[i][j] = str;
            cal.add(Calendar.DAY_OF_YEAR, 1);
        }

current value of j: 0
current value of j: 1
current value of j: 2
current value of j: 3
current value of j: 4
current value of j: 5
current value of j: 6
current value of j: 7 //out of bounds

Answer 4

Your problem is here

calendarTable[i * 2 + 1][j]

if i is equals to 8 then 8 * 2 + 1 = 17 giving you the exception

Answer 5

calendarTable [0] = 7个元素的数组大小（{“ SUNDAY”，“ MONDAY”，“ TUESDAY”，“ WEDNESDAY”，“ THURSDAY”，“ FRIDAY”，“ SATURDAY”}）是否要分配一个值最多写15个项目

Answer 6

It's because of the line:

calendarTable[0] = new String[]{"SUNDAY", "MONDAY", "TUESDAY", "WEDNESDAY", "THURSDAY", "FRIDAY", "SATURDAY"};

calendarTable is an array of arrays. Each row does not necessarily need to have the same number of entries as the one above it. Thus, when you actually do calendarTable[0] = new String[] , you're telling Java to replace the array at calendarTable[0] with a new one that only has 7 entries, which is why it goes over bounds.

Theoretically, nothing is stopping you from also doing this:

   calendarTable[1] = new String[]{"One Entry"};

It's legal. calendarTable[0].length is 7, and calendarTable[1].length is 1.

I don't know what you're trying to achieve in this program, but you either need to do something like this:

calendarTable[0][0] = "SUNDAY";
calendarTable[0][1] = "MONDAY";
calendarTable[0][2] = "TUESDAY";
calendarTable[0][3] = "WEDNESDAY";
calendarTable[0][4] = "THURSDAY";
calendarTable[0][5] = "FRIDAY";
calendarTable[0][6] = "SATURDAY";

or something like this:

calendarTable[0] = new String[]{"SUNDAY", "MONDAY", "TUESDAY", "WEDNESDAY", "THURSDAY", "FRIDAY", "SATURDAY", "", "", "", "", "", "", "", "", ""};