Rookie mistakes in computer programming

At work, I fell short of my usual high standards a couple of times lately, and found both interesting in that they relate to switching between languages.

I have a lot of experience in Java. I haven't used C++ much ( and I found it can be a mistake to write C++ while thinking in Java. )

I've used Python rather more recently ( and found that it, too, is not enhanced by one's thinking in Java. )