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Random Number Problem

10 replies on 1 page. Most recent reply: Feb 24, 2003 4:23 PM by Matt Gerrans

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Flat View: This topic has 10 replies on 1 page

AgentCyan

Posts: 9
Nickname: sulfricyan
Registered: Feb, 2003

Random Number Problem

Posted: Feb 12, 2003 2:19 PM

For some reason i keep getting the same random number every time the program runs.

How do i fix this?

My code for the random number is a follows:

int random = (int) (Math.random() * 100);

thanks

Matt Gerrans

Posts: 1153
Nickname: matt
Registered: Feb, 2002

Re: Random Number Problem

Posted: Feb 12, 2003 4:56 PM

Well, that is, of course, possible, just not very probable. I would guess that the Math module always seeds the Random object it creates with the time, so maybe your system clock is in limbo. Chances are it is a bug in your code. Let's see the rest of it.

Matt Gerrans

Posts: 1153
Nickname: matt
Registered: Feb, 2002

Re: Random Number Problem

Posted: Feb 12, 2003 4:57 PM

Ye gads! I just read that first sentence. I think there are more commas than words. How did I ever make it though my college English course? I'm ashamed of myself. I will refrain from using commas for the rest of the day.

AgentCyan

Posts: 9
Nickname: sulfricyan
Registered: Feb, 2003

Re: Random Number Problem

Posted: Feb 12, 2003 5:01 PM

heres the whole program as of now:

import javabook.*;
import java.awt.*;
import java.lang.Math;

public class SecretNumber
{
public static void main (String[] args)
{
int count = 0;
int guess = 0;
int random = (int) (Math.random() * 100);
int trysLeft = 0;
int totalTrys = 6;

do
{
MainWindow mainWindow;
mainWindow = new MainWindow("Welcome To Take A Guess");

InputBox inputBox;
inputBox = new InputBox(mainWindow, "Guess A Number");

guess = inputBox.getInteger("Please Pick A Number Between 0 and 100: ");

if(guess < random)
{
System.out.println("Your Guess Was Too Low.");
count++;
trysLeft = totalTrys - count;
System.out.println("You have " + trysLeft + " guesses left.");
}

if(guess > random)
{
System.out.println("Your Guess Was Too High.");
count++;
trysLeft = totalTrys - count;
System.out.println("You have " + trysLeft + " guesses left.");
}

if(guess == random)
System.out.println("Good Job! You Guessed The Number");

}while(guess != random && trysLeft != 0);

}
}

Matt Gerrans

Posts: 1153
Nickname: matt
Registered: Feb, 2002

Re: Random Number Problem

Posted: Feb 12, 2003 8:08 PM

Doesn't look like it would get a different number every time it runs. Look at it with a debugger or put a

System.out.println( "Hint: " + Integer.toString(random));

right after

int random = (int) (Math.random() * 100);

and you'll see it is usually different.

A few style notes:
- I don't know what the javabook and stuff is, but it looks like GUI stuff; mixing GUI and console output is a bit confusing, but I guess you are just trying to get things working at this point and that is not the final plan.
- I wouldn't import the Math module which has a random method have a variable called random -- that is a bit confusing.
- I would make a special method for generating the magic number to guess. Then it is easy to unit test; so I would then create a test Suite for it, with the Artima SuiteRunner, or JUnit.

Matt Gerrans

Posts: 1153
Nickname: matt
Registered: Feb, 2002

Re: Random Number Problem

Posted: Feb 13, 2003 10:58 AM

Oops, that first sentence should be "It doesn't look like it will get the same number every time it runs."

sunilgiri

Posts: 7
Nickname: sunilgiri
Registered: Feb, 2003

Re: Random Number Problem

Posted: Feb 22, 2003 11:55 AM

That,s ok

Charles Bell

Posts: 519
Nickname: charles
Registered: Feb, 2002

Re: Random Number Problem

Posted: Feb 22, 2003 5:56 PM

When I run your random number generator code on my pc in the following, I do not see the same random number every time the program runs. It sure looks random enough to me.
I don't think your problem is in your java code.


public class RandomNumberTest{
    public static void main (String[] args){
        for (int i = 0; i < 20;i++){
            int random = (int) (Math.random() * 100);
            System.out.print(random + " ");
        }
    }
}

deliquentMind

Posts: 3
Nickname: deliquent
Registered: Feb, 2003

Re: Random Number Problem

Posted: Feb 22, 2003 9:18 PM

try this method:


public double dblRandom(double low, double high) {   
   return Math.random()*(high - low) + low;}

public int intRandom(int low, int high) {   
   int nb = high - low + 1;   
   return (int)(Math.random()*nb + low);
}

[/prep]

to use:

int number = intRandom(1,100);

Oliver

Posts: 12
Nickname: lazycat
Registered: Dec, 2002

Re: Random Number Problem

Posted: Feb 23, 2003 7:32 AM

//try this


        java.util.Random rd = new java.util.Random(System.currentTimeMillis());
        int rndNumber = rd.nextInt(100) + 1;

Matt Gerrans

Posts: 1153
Nickname: matt
Registered: Feb, 2002

Re: Random Number Problem

Posted: Feb 24, 2003 4:23 PM

It's not necessary to seed the random number gererator; if you look at the documentation you'll see that it is done by default.

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