Improving the algorithm
Figure 307. Implementation observation 
101 / 2 = 50.5
101 / 3 = 33.6...
101 / 4 = 25.25
101 / 5 = 20.20
101 / 6 = 16.83...
101 / 7 = 14.43...
101 / 8 = 12.625
101 / 9 = 11.2...
101 / 10 = 10.1
101 / 11 = 9.18...
101 / 12 = 8.4...
101 / 13 = 7.7...
...Figure 308. Changing the implementation
Big performance gain:
public static boolean isPrime(int value) {
for (int i = 2; i * i < value; i++) {
if (0 == value % i) {
return false;
}
}
return value != 1;
}Figure 309. Regression test
Figure 311. Error correction in detail
public static boolean isPrime(int value) {
//for (int i = 2; i * i < value; i++) {
for (int i = 2; i * i <= value; i++) {
if (0 == value % i) {
return false;
}
}
return value != 1;
}