使用Apache Lang3 Commons

Integer.parseInt(RandomStringUtils.randomNumeric(6, 6));

最小值100000到最大值999999

我已经创建了一个方法来获取给定范围内的唯一整数。

/*
      * minNum is the minimum possible random number
      * maxNum is the maximum possible random number
      * numbersNeeded is the quantity of random number required
      * the give method provides you with unique random number between min & max range
*/
public static Set<Integer> getUniqueRandomNumbers( int minNum , int maxNum ,int numbersNeeded ){

    if(minNum >= maxNum)
        throw new IllegalArgumentException("maxNum must be greater than minNum");

    if(! (numbersNeeded > (maxNum - minNum + 1) ))
        throw new IllegalArgumentException("numberNeeded must be greater then difference b/w (max- min +1)");

    Random rng = new Random(); // Ideally just create one instance globally

    // Note: use LinkedHashSet to maintain insertion order
    Set<Integer> generated = new LinkedHashSet<Integer>();
    while (generated.size() < numbersNeeded)
    {
        Integer next = rng.nextInt((maxNum - minNum) + 1) + minNum;

        // As we're adding to a set, this will automatically do a containment check
        generated.add(next);
    }
    return generated;
}

以下代码生成100000到900000之间的随机数。此代码将生成六位数的值。我用这个代码生成一个六位数的OTP。

使用importjava.util.Random来使用此随机方法。

import java.util.Random;

// Six digits random number generation for OTP
Random rnd = new Random();
long longregisterOTP = 100000 + rnd.nextInt(900000);
System.out.println(longregisterOTP);

可以使用以下代码：

ThreadLocalRandom.current().nextInt(rangeStart, rangeEndExclusive)

只需执行以下语句即可完成：

Randomizer.generate(0, 10); // Minimum of zero and maximum of ten

下面是它的源代码。

文件Randomizer.java

public class Randomizer {
    public static int generate(int min, int max) {
        return min + (int)(Math.random() * ((max - min) + 1));
    }
}

它只是干净和简单。

我正在考虑使用以下方法将生成的随机数线性归一化到所需范围。设x为随机数，设a和b为期望归一化数的最小和最大范围。

下面是一个非常简单的代码片段，用来测试线性映射产生的范围。

public static void main(String[] args) {
    int a = 100;
    int b = 1000;
    int lowest = b;
    int highest = a;
    int count = 100000;
    Random random = new Random();
    for (int i = 0; i < count; i++) {
        int nextNumber = (int) ((Math.abs(random.nextDouble()) * (b - a))) + a;
        if (nextNumber < a || nextNumber > b) {
            System.err.println("number not in range :" + nextNumber);
        }
        else {
            System.out.println(nextNumber);
        }
        if (nextNumber < lowest) {
            lowest = nextNumber;
        }
        if (nextNumber > highest) {
            highest = nextNumber;
        }
    }
    System.out.println("Produced " + count + " numbers from " + lowest
            + " to " + highest);
}