code: protected final void checkResize() {
          if (size == table.length) { // size / table.length > DENSITY
              int forSize = table.length + 1; // size + 1;
              for (int i=0, newCapacity = MIN_CAPA; i < PRIMES.length; i++, newCapacity <<= 1) {
                  if (newCapacity > forSize) {
                      resize(PRIMES[i]);
                      return;
                  }
              }
              return;
          }
      }
docs: private static final int DENSITY = 5;