June 2001
Intermediate to advanced
888 pages
21h 1m
English
The
array filled up, and you got an
ArrayIndexOutOfBoundsException
.
Make the array bigger.
One approach is to allocate the array at a reasonable size to begin with, but if you find yourself with more data than will fit, reallocate a new, bigger array and copy the elements into it.[22] Here is code that does so:
import java.util.*;
/** Re-allocate an array, bigger... */
public class Array2 {
public static void main(String argv[]) {
int nDates = 0;
final int MAX = 10;
Calendar dates[] = new Calendar[MAX];
Calendar c;
while ((c=getDate( )) != null) {
// if (nDates >= dates.length) {
// System.err.println("Too Many Dates! Simplify your life!!");
// System.exit(1); // wimp out
// }
// better: reallocate, making data structure dynamic
if (nDates >= dates.length) {
Calendar tmp[] = new Calendar[dates.length + 10];
System.arraycopy(dates, 0, tmp, 0, dates.length);
dates = tmp; // copies the array reference
// old array will be garbage collected soon...
}
dates[nDates++] = c;
}
System.out.println("Array size = " + dates.length);
}
static int n;
/* Dummy method to return a sequence of 21 Calendar references,
* so the array should be sized >= 21.
*/
public static Calendar getDate( ) {
if (n++ > 21)
return null;
return Calendar.getInstance( );
}
}This technique will work reasonably well for simple linear collections of data. For data with a more variable structure, you will probably want to use a more dynamic approach, as in Section 7.4.
[22]