Anonymous
Anonymous asked in Computers & InternetProgramming & Design · 8 years ago

# Proper use of Java's Math.random() function?

I have a quick question about how to use the function Math.random() properly.

Lets say I wanted to make a random number between 1 and 10, I know to do this I need to use the following code;

(int)(Math.random() * 10) + 1

Is the "+ 1" at the end is necessary seeing as I already have "(int)" at the front? And if I were to take out the "+ 1" would it create a random number between 0 and 10, instead of 1 and 10?

Relevance
• 8 years ago

As Baatus says, if you want random ints it's better to use the random class:

Random rand = new Random();

int rNum = rand.nextInt(10) + 1;

Because

nextInt(k)

returns 0 through k-1, inclusive. So nextInt(10) is 0-9, adding the 1 gives 1-10.

don't forget to

import java.util.Random;

• ?
Lv 5
8 years ago

actually .random() returns a number between 0 and 1 and is actually real. You multiply by the end of the interval and add the begining. So for example if I wanted to generate a number between 3 and 20 I would use

Math.random() * 20 + 3

basically it's .random() * max + min

since it's between 0 and 1. So the 1 turns into the max and you push the 0 to wherever you need (like 1 or 3 etc.)

• Anonymous
8 years ago

I always do

Random r=new Random();

int i= r.nextInt(10)+1;