从Date.getTime（）计算日期/时间

Question

我根据调用事务的日期/时间计算事务ID。因此我使用.getTime（）将Date对象转换为long num，代码如下

public long calcTransactionID (Date myDate)
{
    long transactionID;
    transactionID = myDate.getTime();
    return long;
}

完美无缺。现在我该怎么做反过来，给定事务ID我想得到Date对象（或者至少是字符串中的日期/时间）。

public getDateFromTrans (long transactionID)
{
    ???
    return myDate;
}

是否可以使用Date.getTime（）？

构造日期对象

Answer 1

尝试：

public Date getDateFromTrans (long transactionID)
{
    return new Date(transactionID);
}

Answer 2

您也可以使用java.util.Calendar，因为：

public void writeDateAndTime(long transactionId) {
    Calendar calendar = Calendar.getInstance();
    calendar.setTimeInMillis(transactionId);

    // this is how to get each part
    int year = calendar.get(Calendar.YEAR);
    int month = Calendar.get(Calendar.MONTH);
    int day = Calendar.get(Calendar.DAY_OF_MONTH);
    int hour = Calendar.get(Calendar.HOUR_OF_DAY);
    int minute = Calendar.get(Calendar.MINUTE);
    int second = Calendar.get(Calendar.SECOND);

    // and this is how to get a java.util.Date object
    Date date = Calendar.getTime();
}