title: What is wrong with my isPrime method?
body: <p>This is my <code>isPrime</code> method:</p>
  
  <pre><code>private static boolean isPrime(int num) {
      if (num % 2 == 0) return false;
      for (int i = 3; i * i &lt; num; i += 2)
          if (num % i == 0) return false;
      return true;
  }
  </code></pre>
  
  <p>I put <code>isPrime(9)</code> and it returns <code>true</code>. What is wrong with the method?</p>