&gt; Junior dev<p>&gt; Monolithic java codebase<p>&gt; &quot;we already wrote something similar&quot;<p>Sometimes it&#x27;s not even them who wrote something.  I was working on a Java codebase where decimal numbers always had the separator be a period (e.g. 1.2).<p>In (most of) continental Europe, the character they use to separate the numbers in a decimal is a comma (e.g. 1,2).  So I coded something up to do a location-specific separator.<p>Woops!  Actually java.text.DecimalFormatSymbols().getDecimalSeparator() will do that, and has been a Java core API since Java 1.1.