favorite favourite

What's your favourite standard library function?

Mine is Matlab's squeeze. Every time I use it I can imagine my hyperdimensional manifestation pushing the matrix until all those useless dimensions become shiny drops of acid that are slowly absorbed into the surrounding space.

JOptionPane. It's like cout and MsgBox but customizable. I always build a wrapper around it, name it "say()" and pass stuff to it that the user should know. You can even make a password input field if you inject a pane into one. Take that, DOS!

In java, it does annoy me that console I/O is convoluted. Fuckers couldn't put a cout and cin at the top of the namespace, and you have to cringe and dig deep into IO structure APIs and object passing when teaching the language to a prospective disciple who knows his easier C / C++ I/O. wtf