How to get a random number between 10 and 20

Newbie & Debugging Questions
#1

Alright i am currently making a text based RPG and im having trouble making a random number between like lets say 10 and 20.

I currently know how to make random numbers between 0 and a number.

this is the code i use to get a random number between 0 and 20.

roll = (int)(Math.random() * 20);

what i need is a number between 10 and 20 any help on how to do this would be nice.

#2

I like easy questions :slight_smile:
Random r = new Random();
roll = r.nextInt() % 10 + 10;

#3

so that would make it between 10 and 20 right…

so if i wanted to make it between 20 and 50 would i just do this?
roll = r.nextInt() % 20 + 30;

#4

i tried what you did and it worked for a number between 10 and 20 but then when i tried getting between 20 and 25 i did r.nextInt() % 20 + 5; and i got -8 lol…

#5 

Random rand = new Random()

int number = rand.nextInt(10) + 10;  // number from 10 to 19 inclusive
int number = rand.nextInt(11) + 10;  // number from 10 to 20 inclusive
int number = rand.nextInt(6) + 20;  // number from 20 to 25 inclusive

The number inside the nextInt is the range of numbers that you want. The number added after is the bottom of that range.

#6

That gives you 0 to 19 (inclusive).

random.nextInt(20)+1

Gives you 1 to 20 (inclusive). Like a typical 20 sided dice would do.

random.nextInt(biggestPossibleValue+1)+smallestPossibleValue

Gives you smallestPossibleValue to biggestPossibleValue (inclusive, of course).

#7

Thank you for the help. i have 1 other questionthough and i might sound stupid but how do you get all the class files and pictures for a JFrame into an executable jar file?

#8

If you are using Eclipse then easiest way is to Right-Click on your project (in Package Explorer)… Then ‘Export’ --> Java ‘JAR file’ etc…
After which you can select with pictures/classes you want to include.

#9

thank you i will try that

#10

public int rand(int s, int e) {
return (s + (int) (Math.random() * (e-s)));
}

#11

Not quite.

random.nextInt((biggestPossibleValue-smallestPossibleValue)+1)+smallestPossibleValue

Gives you smallestPossibleValue to biggestPossibleValue (inclusive, of course).

#12

Heh. That happened because I was unable to find a nice name for deltaThing… and then I thought… hey, using the biggest possible value would be nicer… but I didn’t pay enough attention. :wink: