class CountWheat {
public static void main (String args[]) {
int i, j, k;
j = 1;
k = 0;
for (i=1; i <= 64; i++) {
j *= 2;
k += j;
System.out.print(k + "\t ");
if (i%4 == 0) System.out.println();
}
System.out.println("All done!");
}
}
% javac CountWheat.java % java CountWheat javac CountWheat.java java CountWheat % 2 6 14 30 62 126 254 510 1022 2046 4094 8190 16382 32766 65534 131070 262142 524286 1048574 2097150 4194302 8388606 16777214 33554430 67108862 134217726 268435454 536870910 1073741822 2147483646 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 -2 All done! %What happened? After 2,147,483,646 grains of wheat were counted the next number should have been 6,442,450,938. However an int canšt be larger than 2,147,483,647. The number instead wrapped around into the negative numbers and stayed there.
You can improve your results slightly (but only slightly) by changing the ints to longs. A long is an integer type variable that can hold up to 9,223,372,036,854,775,807. However even that isn't enough to count how much wheat the king owed. To truly calculate the kingšs debt use a double, the largest type of all.