Solved

Getting a random sign

Posted on 2004-08-03
10
484 Views
Last Modified: 2006-11-17
Hi all,

I want to get a randomly generated binary choice:  either -1 or 1.  This function does it, but is there is a 'nicer' way?

  private int getRandomSign() {
    if (Math.random() <= 0.5) return -1;
      else return 1;
    }
  }
0
Comment
Question by:Dawkins
  • 3
  • 2
  • 2
  • +2
10 Comments
 
LVL 14

Assisted Solution

by:sudhakar_koundinya
sudhakar_koundinya earned 25 total points
ID: 11706737
That is the nicer way :)
0
 
LVL 35

Expert Comment

by:girionis
ID: 11707086
Can you define "nicer"? Your code looks fine.
0
 
LVL 35

Accepted Solution

by:
girionis earned 25 total points
ID: 11707122
Maybe you could do

 private int getRandomSign() {
    if (Math.random() < 0.5) return -1;
      else return 1;
    }
  }

since it can return a value equal to zero but never one.
0
Microsoft Certification Exam 74-409

Veeam® is happy to provide the Microsoft community with a study guide prepared by MVP and MCT, Orin Thomas. This guide will take you through each of the exam objectives, helping you to prepare for and pass the examination.

 
LVL 14

Expert Comment

by:sudhakar_koundinya
ID: 11707291
I haven't understand the difference between if (Math.random() < 0.5) return -1; and if (Math.random() <= 0.5) return -1;

both results gives the value less than one only.

Regards
Sudhakar
0
 

Author Comment

by:Dawkins
ID: 11707310
>>>  Maybe you could do...

Good point, it should be < rather than <=. I'll change that

>>> Can you define "nicer"? Your code looks fine.

well basically I am teaching myself how to program in Java and know no Java programers in real life so have no one to ask "is this completely ridiculous", so I come here instead :)  By nicer I mean "more elegant, simpler, less code, there's already a java library function that does that" etc

Seems like I've already found the best way so I'll give it another 30 minutes to make sure and then give you two the points.
0
 
LVL 6

Expert Comment

by:rpnman
ID: 11707336

Here's another approach that may be closer to what you want:

private int getRandomSigh() {
    return (int) (Math.signum(0.5-Math.random())) ;
}

An additional note:  using "<= 0.5" favors -1  VERY slightly  since Math.random() returns values between 0 and .999...
0
 
LVL 6

Expert Comment

by:rpnman
ID: 11707408
There's a problem with my posted solution: there's a very slight chance it will return 0. If you can't live with that, here's an amendment:


private int getRandomSign() {
    int sign = (int) (Math.signum(0.5-Math.random())) ;
    return sign = 0 ? 1 : sign ;
}
0
 
LVL 15

Expert Comment

by:JakobA
ID: 11707712
nice & short:

private int getRandomSign() {
    return (Math.random()<0.5) ? 1 : -1;                           // ?: operator same as in C
}

regards JakobA
0
 

Author Comment

by:Dawkins
ID: 11708880
Thanks everyone, I'll keep it as I originally had it but put < 0.5 instead to ensure the split is exactly 50/50
0
 
LVL 35

Expert Comment

by:girionis
ID: 11712677
:)
0

Featured Post

3 Use Cases for Connected Systems

Our Dev teams are like yours. They’re continually cranking out code for new features/bugs fixes, testing, deploying, testing some more, responding to production monitoring events and more. It’s complex. So, we thought you’d like to see what’s working for us.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
jar file executable 12 52
print map entry 34 69
how to install java on RHEL image on EC2 4 30
hibernate jars 4 32
An old method to applying the Singleton pattern in your Java code is to check if a static instance, defined in the same class that needs to be instantiated once and only once, is null and then create a new instance; otherwise, the pre-existing insta…
Introduction Java can be integrated with native programs using an interface called JNI(Java Native Interface). Native programs are programs which can directly run on the processor. JNI is simply a naming and calling convention so that the JVM (Java…
Viewers will learn one way to get user input in Java. Introduce the Scanner object: Declare the variable that stores the user input: An example prompting the user for input: Methods you need to invoke in order to properly get  user input:
This tutorial covers a step-by-step guide to install VisualVM launcher in eclipse.

831 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question