java 如何创建一个随机的 16 位数字，具有特定的第一位数字？
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How to create a random 16 digits number, with specific first digits?
提问by Marios Ath
I want to create a randomly generated 16 digit-number in java.But there is a catch I need the first two digits to be "52". For example, 5289-7894-2435-1967. I was thinking of using a random generator and create a 14 digit number and then add an integer 5200 0000 0000 0000. I tried looking for similar problems and can't really find something useful. I'm not familiar with the math method,maybe it could solve the problem for me.
我想在java中创建一个随机生成的16位数字。但是有一个问题，我需要前两位数字为“52”。例如，5289-7894-2435-1967。我正在考虑使用随机生成器并创建一个 14 位数字，然后添加一个整数 5200 0000 0000 0000。我尝试寻找类似的问题，但找不到真正有用的东西。我对数学方法不熟悉，也许它可以为我解决问题。
采纳答案by Fund Monica's Lawsuit
First, you need to generate a random 14-digit number, like you've done:
首先，您需要生成一个随机的 14 位数字，就像您所做的那样：
long first14 = (long) (Math.random() * 100000000000000L);
Then you add the 52at the beginning.
然后52在开头添加。
long number = 5200000000000000L + first14;
One other way that would work equally well, and will save memory, since Math.random()creates an internal Randomobject:
另一种同样有效并节省内存的方法，因为Math.random()创建了一个内部Random对象：
//Declare this before you need to use it
java.util.Random rng = new java.util.Random(); //Provide a seed if you want the same ones every time
...
//Then, when you need a number:
long first14 = (rng.nextLong() % 100000000000000L) + 5200000000000000L;
//Or, to mimic the Math.random() option
long first14 = (rng.nextDouble() * 100000000000000L) + 5200000000000000L;
Note that nextLong() % nwill not provide a perfectly random distribution, unlike Math.random(). However, if you're just generating test data and it doesn't have to be cryptographically secure, it works as well. It's up to you which one to use.
请注意nextLong() % n，与 不同，它不会提供完美的随机分布Math.random()。但是，如果您只是生成测试数据并且它不必是加密安全的，那么它也能正常工作。使用哪一种取决于您。
回答by weston
Random rand = new Random();
String yourValue = String.format((Locale)null, //don't want any thousand separators
"52%02d-%04d-%04d-%04d",
rand.nextInt(100),
rand.nextInt(10000),
rand.nextInt(10000),
rand.nextInt(10000));
回答by sol4me
You can generate 14 random digits and then append at the beginning "52". E.g.
您可以生成 14 个随机数字，然后在开头附加“52”。例如
public class Tes {
public static void main(String[] args) {
System.out.println(generateRandom(52));
}
public static long generateRandom(int prefix) {
Random rand = new Random();
long x = (long)(rand.nextDouble()*100000000000000L);
String s = String.valueOf(prefix) + String.format("%014d", x);
return Long.valueOf(s);
}
}
回答by Jordi Castilla
- Create a 14 random digit number. with
Math.random - Concatenate to it at the begining the "52"
String. - Convert the string with
Integer.parseInt(String)method
- 创建一个 14 位随机数字。和
Math.random - 在 "52" 开头连接它
String。 - 用
Integer.parseInt(String)方法转换字符串
