CODEWITHSUNDEEP
javamathrandom
Learner
Learner

Reputation: 2339

How to generate random values between -1/2 to 1/2

I am trying to figure out a way to generate random values between 1/2 and -1/2.

I tried something as below, but not sure if this is a right way to do it....

Can someone please let me know a good way to implement this?

public static void main(String args[]) {
        double Max = .5;
        double Min = -0.5;
        for (int i = 0; i < 10000; i++) {
            double value = Min + ((Math.random()) * (Max - Min));
            System.out.println(value);
        }
    }

Upvotes: 3

Views: 913

Answers (3)

arshajii
arshajii

Reputation: 129587

Well Math.random() returns a random double between 0 and 1, so to change the range to -1/2 to 1/2, we can just subtract 1/2 (since 0 - 1/2 = -1/2 and 1 - 1/2 = 1/2):

Math.random() - 0.5

What you are doing now is more general, i.e. if you want a double between min and max the appropriate expression would be

min + Math.random() * (max - min)

In this case, plugging in min = -0.5 and max = 0.5 we have

-0.5 + Math.random() * (0.5 - -0.5)

which simplifies to

Math.random() - 0.5

I should also mention that, if you read the random() method's documentation, you will find that it returns a double greater than or equal to 0.0 and less than 1.0. This means that the expression above should produce a number in the range [-0.5, 0.5), meaning that -0.5 can potentially be returned but 0.5 cannot be.

Upvotes: 9

user2280897
user2280897

Reputation: 89

Bear in mind that the Math.Random() class is going to return a value between 0 and 1, not including 1.

In this case, Math.Random()-0.5 will work sweetly

Upvotes: 1

tckmn
tckmn

Reputation: 59363

You could just do:

Math.random() - 0.5

This is because the min of Math.random() is 0, and the max is 1. If you subtract a half, the min will be 0 - 0.5 == -0.5 and the max will be 1 - 0.5 == 0.5.

Therefore, your original code can be shortened to:

public static void main(String args[]) {
    for (int i = 0; i < 10000; i++) {
        double value = Math.random() - 0.5; // no need for a "double" cast,
                                            // Math.random() returns a double
        System.out.println(value);
    }
}

Upvotes: 5

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