How do I write a Java program that can get the time between my keyboard key-presses?

So my main objective is to create a new Random number generating function that will generate a random number with the help of human randomness. I want to be able to get the time between previous keystrokes that were entered by the user and save them in some sort of a float or double variable.

While trying to create such a program, I thought about using a pointer to get the address of a variable that is random every time and thought I could proceed with that. But apparently Java doesn't support pointers so here I am, trying to get a new idea for generating random numbers.