根据给定的数字集在Java中生成随机数

Question

Is it possible to generate random no. from the given set of no. like 5, 50, 20? If so please give simple example thanks.

Answer 1

Here's one way to do it.

import java.util.concurrent.ThreadLocalRandom;

class randomFromList {
    public static void main(String[] args) {
        int x = 0;
        int[] arr = {5, 50, 20}; // any set of numbers of any length
        for (int i = 0; i < 100; i++) { // prints out 100 random numbers from the list
            x = ThreadLocalRandom.current().nextInt(0, arr.length); // random number
            System.out.println(arr[x]); // item at random index
        }    
    }
}

It is better to use java.util.concurrent.ThreadLocalRandom as of Java 1.7+. See here for why. However, if you're using a version that predates Java 1.7, use Random

Answer 2

public class RandomNumbers {

  public static void main(String[] args) {
    int[] randomNumbers = new int[] { 2, 3, 5, 7, 11, 13, 17, 19 };

    Random r = new Random();
    int nextRandomNumberIndex = r.nextInt(randomNumbers.length);
    System.out.println(randomNumbers[nextRandomNumberIndex]);
  }

}

Answer 3

You can use Random.nextInt() to get a random index .

Use that index to get you pseudo random element:

int[] arr = {1, 2, 3};
int randomIndex = Random.nextInt(arr.length);
int randomVal = arr[randomIndex];