生成13至100之间的1000个随机数

Question

I'm trying to generate 1000 random numbers between 13 and 100. So far it's only generating 75% of what I want repeatedly a thousand times. Here's what I have so far:

Random rand = new Random();
for (int j = 0; j < 1000; j++)
{
    int pick = rand.nextInt((87) + 13);
    pick++;
}

Why isn't it working?

Answer 1

Pay attention to nextInt() covering the 0 inclusively and the specified value exclusively ! So it has to be rand.nextInt(88) to make the highest int generated be 87. Here is what you want:

Random rand = new Random();
for (int j = 0; j<1000; j++)
{
    int pick = rand.nextInt(88)+13;
}

Answer 2

rand.nextInt(88) + 13; should give you numbers between 13 and 100, and you just put it in your loop.

Answer 3

The line :

So far its only generating 75% of what i want repeatedly a thousand times

Really doesn't add up to me. It might be a seeding issue you're having though. Make sure to always re-seed the random number, using time.

But I agree with Abdul , you need to take the +13 out of that parenthesis:

rand.nextInt(87) + 13;

Because rand.nextInt((87) + 13) is the same as rand.nextInt((67) + 23) as rand.nextInt((1) + 99)

But if you want more "true" randomness, look into something called buzzhash (though that is for hashing ; yet may be modded for number)

Answer 4

I use this in my codes:

public static int randomInteger(int min, int max)
{
    java.security.SecureRandom rand = new java.security.SecureRandom();

    //get bounded [0, max) from nextInt()
    int randomNum = rand.nextInt(max) + min;

    return randomNum;
}

value = randomInteger(13,100); //13..99
value = randomInteger(13,101); //13..100