在java中生成10位唯一随机数 [英] Generating 10 digits unique random number in java

问题描述

我正在尝试使用以下代码生成10位唯一随机数。根据我的要求，我必须创建大约5000个唯一数字（ID）。这没有按预期工作。它还会生成-ve数字。此外，有时生成的数字中缺少一个或两个数字，导致8或9个数字不是10.

I am trying with below code to generate 10 digits unique random number. As per my req i have to create around 5000 unique numbers(ids). This is not working as expected. It also generates -ve numbers. Also sometimes one or two digits are missing in generated number resulting in 8 or 9 numbers not 10.

public static synchronized  List generateRandomPin(){

    int START =1000000000;
    //int END = Integer.parseInt("9999999999");
    //long END = Integer.parseInt("9999999999");
    long END = 9999999999L;

    Random random = new Random();

    for (int idx = 1; idx <= 3000; ++idx){
        createRandomInteger(START, END, random);
    }

    return null;
}


private static void createRandomInteger(int aStart, long aEnd, Random aRandom){
    if ( aStart > aEnd ) {
      throw new IllegalArgumentException("Start cannot exceed End.");
    }
    //get the range, casting to long to avoid overflow problems
    long range = (long)aEnd - (long)aStart + 1;
    logger.info("range>>>>>>>>>>>"+range);
    // compute a fraction of the range, 0 <= frac < range
    long fraction = (long)(range * aRandom.nextDouble());
    logger.info("fraction>>>>>>>>>>>>>>>>>>>>"+fraction);
    int randomNumber =  (int)(fraction + aStart);    
    logger.info("Generated : " + randomNumber);

  }

推荐答案

我认为您获得8/9位数值和负数的原因是您要添加分数，长 （带符号的64位值），可能大于正 int 范围（32位值）到 aStart 。

I think the reason you're getting 8/9 digit values and negative numbers is that you're adding fraction, a long (signed 64-bit value) which may be larger than the positive int range (32-bit value) to aStart.

该值溢出，使得 randomNumber 处于负32位范围内或几乎已经包含在内 aStart （因为 int 是带符号的32位值，分数只需稍微小于（2 ^ 32 - aStart ），即可看到8位或9位数值。）

The value is overflowing such that randomNumber is in the negative 32-bit range or has almost wrapped around to aStart (since int is a signed 32-bit value, fraction would only need to be slightly less than (2^32 - aStart) for you to see 8 or 9 digit values).

您需要使用 long 获取所有值。

You need to use long for all the values.

   private static void createRandomInteger(int aStart, long aEnd, Random aRandom){
    if ( aStart > aEnd ) {
      throw new IllegalArgumentException("Start cannot exceed End.");
    }
    //get the range, casting to long to avoid overflow problems
    long range = aEnd - (long)aStart + 1;
    logger.info("range>>>>>>>>>>>"+range);
    // compute a fraction of the range, 0 <= frac < range
    long fraction = (long)(range * aRandom.nextDouble());
    logger.info("fraction>>>>>>>>>>>>>>>>>>>>"+fraction);
    long randomNumber =  fraction + (long)aStart;    
    logger.info("Generated : " + randomNumber);

  }

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