random_examples - matthew9510/Studies GitHub Wiki

The Random Object

Basics

import java.util.Random; makes Java's Random class available to the program.

Random rand = new Random(); creates a new random number generator object named rand. The method call rand.nextInt(X) can then be used to get a random number ranging from 0 to X - 1.

Uses of the new Object named rand:

rand.nextInt(), with no number between the (), returns a random value that could be any integer (of int type), positive or negative.

rand.nextInt(10) produces a random number between 0 and 9.

rand.nextInt(maxNum - minNum + 1) + minNum The code adds 1 to obtain a random value between minNum and maxNum.

rand.nextInt( 9 - 0 + 1) + 1 The code adds 1 to obtain values between 1 and 9.

Making a pseudo-random number generator

A pseudo-random number generator produces a specific sequence of numbers based on a seed number, that sequence seeming random but always being the same for a given seed.

Random() seeds the pseudo-random number generator with a number based on the current time. That number is essentially random, so the program will get a different pseudo-random number sequence on each run.
Random(num) will seed the generator with the value num, where num is any integer (actually, any "long" value).

An important part of testing or debugging a program is being able to have the program run exactly the same across multiple runs, most programming languages use a pseudo-random number generation approach to solve this problem.