Once an array is created, its size cannot be changed.
If you want to change the size, you must create a new array and populates it using the values of the old array.
public class MainClass {
public static void main(String[] args) {
int[] numbers = { 1, 2, 3 };
int[] temp = new int[4];
int length = numbers.length;
for (int j = 0; j < length; j++) {
temp[j] = numbers[j];
}
numbers = temp;
}
}