什么时候应该使用Double.longBitsToDouble（...）而不是简单地将long强制转换为double？

Question

I have an array of double values where the last one will be in fact a long representing time in milliseconds. Therefore this long needs to be converted to a double to fit into the array. Later at the time of retrieval of this long value it needs to be converted back to a long type. It is critical that the long value after retrieval from the array of doubles is exactly the same value (down to a one millisecond) I had before putting it into the array. There will be no operations whatsoever performed on the long value while in the array. So the questions are:
Should I simply cast the long value to double and upon retrieval cast it back to long? Will this preserve the exact value of my long?
Or should I use Double.longBitsToDouble(time) method to put the long into the array and retrieve it with Double.doubleToLongBits(time).
Or maybe I should put the long value into the array using Double.longBitsToDouble(time) and retrieve the encoded long by simply casting it to long type?
Thank you in advance for your help.

Answer 1

I mean, what you should do is to not use an array to represent values meaning different things...

But from what it sounds like, you have no choice but to use Double.longBitsToDouble , since a double cannot give you full precision on all long values. Just casting a long to double will lose precision.

Answer 2

I would create a custom class that is basically a container for a double array and a single long value. You should never use arrays for storing data of different types or with the intention of using certain elements of the array for different purposes.

Example using a List<double> :

public class DoublesWithTimestampStructure
{
    private List<double> doubles;
    private long timestamp;

    public DoublesWithTimestampStructure()
    {
        this.doubles = new List<double>();
        this.timestamp = 0;
    }

    /*
    ... getter and setter methods, miscellaneous methods, etc.
    */
}