关于java:生成随机出生日期

Generate random date of birth

我试图用Java程序在数据库中生成一个随机的出生日期。我该怎么做?


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import java.util.GregorianCalendar;

public class RandomDateOfBirth {

    public static void main(String[] args) {

        GregorianCalendar gc = new GregorianCalendar();

        int year = randBetween(1900, 2010);

        gc.set(gc.YEAR, year);

        int dayOfYear = randBetween(1, gc.getActualMaximum(gc.DAY_OF_YEAR));

        gc.set(gc.DAY_OF_YEAR, dayOfYear);

        System.out.println(gc.get(gc.YEAR) +"-" + (gc.get(gc.MONTH) + 1) +"-" + gc.get(gc.DAY_OF_MONTH));

    }

    public static int randBetween(int start, int end) {
        return start + (int)Math.round(Math.random() * (end - start));
    }
}


java.util.Date有一个自epoch以来接受毫秒数的构造函数,java.util.Random有一个方法可以给您随机的毫秒数。您将希望根据所需的dobs范围为随机值设置一个范围,但应该这样做。

非常粗略地说:

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Random  rnd;
Date    dt;
long    ms;

// Get a new random instance, seeded from the clock
rnd = new Random();

// Get an Epoch value roughly between 1940 and 2010
// -946771200000L = January 1, 1940
// Add up to 70 years to it (using modulus on the next long)
ms = -946771200000L + (Math.abs(rnd.nextLong()) % (70L * 365 * 24 * 60 * 60 * 1000));

// Construct a date
dt = new Date(ms);


基于Java 8的解决方案的片段:

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Random random = new Random();
int minDay = (int) LocalDate.of(1900, 1, 1).toEpochDay();
int maxDay = (int) LocalDate.of(2015, 1, 1).toEpochDay();
long randomDay = minDay + random.nextInt(maxDay - minDay);

LocalDate randomBirthDate = LocalDate.ofEpochDay(randomDay);

System.out.println(randomBirthDate);

注:这将生成1900年1月1日(含)至2015年1月1日(不含)之间的随机日期。

注:以纪元日为基础,即相对于1970年1月1日(历元)的日数——历元后的正意义,历元前的负意义。

还可以创建一个小型实用程序类:

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public class RandomDate {
    private final LocalDate minDate;
    private final LocalDate maxDate;
    private final Random random;

    public RandomDate(LocalDate minDate, LocalDate maxDate) {
        this.minDate = minDate;
        this.maxDate = maxDate;
        this.random = new Random();
    }

    public LocalDate nextDate() {
        int minDay = (int) minDate.toEpochDay();
        int maxDay = (int) maxDate.toEpochDay();
        long randomDay = minDay + random.nextInt(maxDay - minDay);
        return LocalDate.ofEpochDay(randomDay);
    }

    @Override
    public String toString() {
        return"RandomDate{" +
               "maxDate=" + maxDate +
               ", minDate=" + minDate +
                '}';
    }
}

像这样使用:

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RandomDate rd = new RandomDate(LocalDate.of(1900, 1, 1), LocalDate.of(2010, 1, 1));
System.out.println(rd.nextDate());
System.out.println(rd.nextDate()); // birthdays ad infinitum


你需要定义一个随机日期,对吗?

一种简单的方法是使用long生成一个新的Date对象(从1970年1月1日起以毫秒为单位的时间),然后减去一个随机的long对象:

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new Date(Math.abs(System.currentTimeMillis() - RandomUtils.nextLong()));

(randomutils取自apache commons lang)。

当然,这远不是一个真正的随机日期(例如,你在1970年之前不会得到日期),但我认为这足以满足你的需要。

否则,您可以使用Calendar类创建自己的日期:

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int year = // generate a year between 1900 and 2010;
int dayOfYear = // generate a number between 1 and 365 (or 366 if you need to handle leap year);
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.YEAR, randomYear);
calendar.set(Calendar.DAY_OF_YEAR, dayOfYear);
Date randomDoB = calendar.getTime();


对于java8->assumming,出生数据必须在当天之前:

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import java.time.LocalDate;
import java.time.LocalTime;
import java.time.Period;
import java.time.temporal.ChronoUnit;
import java.util.Random;

public class RandomDate {

    public static LocalDate randomBirthday() {
        return LocalDate.now().minus(Period.ofDays((new Random().nextInt(365 * 70))));
    }

    public static void main(String[] args) {
        System.out.println("randomDate:" + randomBirthday());
    }
}


如果您不介意在代码中添加新的库,可以使用mockneat(免责声明:我是作者之一)。

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MockNeat mock = MockNeat.threadLocal();

// Generates a random date between [1970-1-1, NOW)
LocalDate localDate = mock.localDates().val();
System.out.println(localDate);

// Generates a random date in the past
// but beore 1987-1-30
LocalDate min = LocalDate.of(1987, 1, 30);
LocalDate past = mock.localDates().past(min).val();
System.out.println(past);

LocalDate max = LocalDate.of(2020, 1, 1);
LocalDate future = mock.localDates().future(max).val();
System.out.println(future);

// Generates a random date between 1989-1-1 and 1993-1-1
LocalDate start = LocalDate.of(1989, 1, 1);
LocalDate stop = LocalDate.of(1993, 1, 1);
LocalDate between = mock.localDates().between(start, stop).val();
System.out.println(between);


看这个方法:

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public static Date dateRandom(int initialYear, int lastYear) {
    if (initialYear > lastYear) {
        int year = lastYear;
        lastYear = initialYear;
        initialYear = year;
    }

    Calendar cInitialYear = Calendar.getInstance();
    cInitialYear.set(Calendar.YEAR, 2015);
    long offset = cInitialYear.getTimeInMillis();

    Calendar cLastYear = Calendar.getInstance();
    cLastYear.set(Calendar.YEAR, 2016);
    long end = cLastYear.getTimeInMillis();

    long diff = end - offset + 1;
    Timestamp timestamp = new Timestamp(offset + (long) (Math.random() * diff));
    return new Date(timestamp.getTime());
}


您可以签出随机数发生器以生成随机数据。此库有助于从给定的模型类创建随机数据。签出以下示例代码。

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public class Person {

    @DateValue( from ="01 Jan 1990",to ="31 Dec 2002" , customFormat ="dd MMM yyyy")
    String dateOfBirth;

}

//Generate random 100 Person(Model Class) object
Generator<Person> generator = new Generator<>(Person.class);  
List<Person> persons = generator.generate(100);

因为有许多内置的数据生成器可以使用注释访问,所以您也可以构建自定义的数据生成器。我建议您阅读库页面上提供的文档。


生成随机出生日期:

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import java.util.Calendar;

public class Main {
  public static void main(String[] args) {
    for (int i = 0; i < 100; i++) {
        System.out.println(randomDOB());
    }
  }

  public static String randomDOB() {

    int yyyy = random(1900, 2013);
    int mm = random(1, 12);
    int dd = 0; // will set it later depending on year and month

    switch(mm) {
      case 2:
        if (isLeapYear(yyyy)) {
          dd = random(1, 29);
        } else {
          dd = random(1, 28);
        }
        break;

      case 1:
      case 3:
      case 5:
      case 7:
      case 8:
      case 10:
      case 12:
        dd = random(1, 31);
        break;

      default:
        dd = random(1, 30);
      break;
    }

    String year = Integer.toString(yyyy);
    String month = Integer.toString(mm);
    String day = Integer.toString(dd);

    if (mm < 10) {
        month ="0" + mm;
    }

    if (dd < 10) {
        day ="0" + dd;
    }

    return day + '/' + month + '/' + year;
  }

  public static int random(int lowerBound, int upperBound) {
    return (lowerBound + (int) Math.round(Math.random()
            * (upperBound - lowerBound)));
  }

  public static boolean isLeapYear(int year) {
    Calendar calendar = Calendar.getInstance();
    calendar.set(Calendar.YEAR, year);
    int noOfDays = calendar.getActualMaximum(Calendar.DAY_OF_YEAR);

    if (noOfDays > 365) {
        return true;
    }

    return false;
  }
}

如果您不介意第三方库,则UITLS库有一个随机数据池,它可以从Java 8的日期和时间API生成随机JavaUTL日期和所有日期、时间、瞬间和持续时间。

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LocalDate birthDate = RandomDateUtils.randomPastLocalDate();
LocalDate today = LocalDate.now();
LocalDate under18YearsOld = RandomDateUtils.randomLocalDate(today.minus(18, YEARS), today);
LocalDate over18YearsOld = RandomDateUtils.randomLocalDateBefore(today.minus(18, YEARS));

它位于Maven中央存储库中:

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<dependency>
  <groupId>com.github.rkumsher</groupId>
  utils</artifactId>
  <version>1.3</version>
</dependency>


我认为这将起到关键作用:

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public static void main(String[] args) {
    Date now = new Date();
    long sixMonthsAgo = (now.getTime() - 15552000000l);
    long today = now.getTime();

    for(int i=0; i<10; i++) {
        long ms = ThreadLocalRandom.current().nextLong(sixMonthsAgo, today);

        Date date = new Date(ms);

        System.out.println(date.toString());
    }

}


我是studying Scala,结束Google Java解决方案来选择范围之间的随机日期。我发现这篇文章非常有用,这是我的最终解决方案。希望能对未来的斯卡拉和Java程序员有所帮助。

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import java.sql.Timestamp

def date_rand(ts_start_str:String ="2012-01-01 00:00:00", ts_end_str:String ="2015-01-01 00:00:00"): String = {
    val ts_start = Timestamp.valueOf(ts_start_str).getTime()
    val ts_end = Timestamp.valueOf(ts_end_str).getTime()
    val diff = ts_end - ts_start
    println(diff)
    val ts_rand = new Timestamp(ts_start + (Random.nextFloat() * diff).toLong)
    return ts_rand.toString
}                                         //> date_rand: (ts_start_str: String, ts_end_str: String)String

println(date_rand())                      //> 94694400000
                                              //| 2012-10-28 18:21:13.216

println(date_rand("2001-01-01 00:00:00","2001-01-01 00:00:00"))
                                              //> 0
                                              //| 2001-01-01 00:00:00.0
println(date_rand("2001-01-01 00:00:00","2010-01-01 00:00:00"))
                                              //> 283996800000
                                              //| 2008-02-16 23:15:48.864                    //> 2013-12-21 08:32:16.384