Improving the algorithm

Figure 304. Implementation observation Slide presentation
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 305. Changing the implementation Slide presentation

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 306. Regression test Slide presentation
Regression test

Figure 307. Systematic error debugging Slide presentation

Figure 308. Error correction in detail Slide presentation
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;
}