<p>
The long suffix should always be written in upper case, i.e. 'L', as the lower case 'l' can easily be confused with the digit one '1'.
</p>

<p>
The following code:
</p>

<pre>
long n = 10l;  // Non-Compliant - easily confused with one zero one
</pre>

<p>
should be refactored into:
</p>

<pre>
long n = 10L;  // Compliant
</pre>