Java Random Tutorial (Math.random() vs Random Class nextInt() nextDouble() )

GitHub repo with examples https://github.com/SleekPanther/java-math-improved-random Random numbers are a common part of many programs and games. (Yeah I know they're not truly "random" but pesudorandom numbers are the best computer can do) There are 2 main ways: Using a static method of the built-in Math class, or creating a Random object & calling methods on that object ➣Math.random() -The "Math" class is built-in (no need to import) so calling "Math.random()" gives you a double from 0 to 1 -Not very useful on its own, but the result it can be multiplied to give a "range" of number -"Math.random()*10" gives a range of 10 so 0 through 9.99999 -The upper bound is always excluded so you'd need to add 1 to get an inclusive range -"(int)(Math.random()*10)" casts the result to an integer -or replace "(int)" with "Math.round()" or "Math.floor()" -You can also change the lower bound by adding a number to the end: (int)(Math.random()*10)+10 yields numbers from 10 to 19 (20 is excluded) int min = 5; int max = 15; int range = max - min +1; -Range must be 1 greater than the range you want since the upper bound will always be excluded (int)(Math.random()*range ) +min -This will give you the desired result -Negative values for min & max still work as long as you still add 1 to the range -Getting decimals just involves removing the (int) casting -You might want to round off the numbers to only display a few decimals ➣Random class -Random generator = new Random(); -Creates a new Random object with reference variable "generator" -don't forget to "import java.util.Random;" -You can now use the formula like this: (int)(generator .nextDouble()*range ) +min -Unfortunately nextDouble() can't accept parameters so you basically just use it like Math.random() -generator.nextInt() give you an integer in the range negative 2 billion to positive 2 billion -But you can also use get an integer in a specific range -generator.nextInt(5) yields numbers 0 to 4 (5 is excluded) -The formula can now be used like this -generator.nextInt(range) + min; Details on Random https://docs.oracle.com/javase/7/docs/api/java/util/Random.html Editor I used (Eclipse) https://eclipse.org/downloads/