問題描述
我有一個名為 Student 的對象，它有 studentName、studentId、studentAddress 等.studentId，我必須生成由七個數字字符組成的隨機字符串，例如.
I have an object called Student, and it has studentName, studentId, studentAddress, etc. For the studentId, I have to generate random string consist of seven numeric charaters,
eg.
studentId = getRandomId();
studentId = "1234567" <-- from the random generator.
而且我必須確保沒有重復的 id.
And I have to make sure that there is no duplicate id.
推薦答案
生成一個隨機字符串很容易 - 只需使用 java.util.Random 和一個包含您想要的所有字符的字符串可用，例如
Generating a random string of characters is easy - just use java.util.Random and a string containing all the characters you want to be available, e.g.
public static String generateString(Random rng, String characters, int length)
{
char[] text = new char[length];
for (int i = 0; i < length; i++)
{
text[i] = characters.charAt(rng.nextInt(characters.length()));
}
return new String(text);
}
現在，為了唯一性，您需要將生成的字符串存儲在某處.您如何做到這一點實際上取決于您的應用程序的其余部分.
Now, for uniqueness you'll need to store the generated strings somewhere. How you do that will really depend on the rest of your application.
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