Random.NextDouble Method

[Android.Runtime.Register("nextDouble", "()D", "GetNextDoubleHandler")]
public virtual double NextDouble ();

[<Android.Runtime.Register("nextDouble", "()D", "GetNextDoubleHandler")>]
abstract member NextDouble : unit -> double
override this.NextDouble : unit -> double

Returns

the next pseudorandom, uniformly distributed double value between 0.0 and 1.0 from this random number generator's sequence

Attributes

RegisterAttribute

Remarks

Returns the next pseudorandom, uniformly distributed double value between 0.0 and 1.0 from this random number generator's sequence.

The general contract of nextDouble is that one double value, chosen (approximately) uniformly from the range 0.0d (inclusive) to 1.0d (exclusive), is pseudorandomly generated and returned.

The method nextDouble is implemented by class Random as if by:

{@code
            public double nextDouble() {
              return (((long)next(26) << 27) + next(27))
                / (double)(1L << 53);
            }}

The hedge "approximately" is used in the foregoing description only because the next method is only approximately an unbiased source of independently chosen bits. If it were a perfect source of randomly chosen bits, then the algorithm shown would choose double values from the stated range with perfect uniformity.

[In early versions of Java, the result was incorrectly calculated as:

{@code
              return (((long)next(27) << 27) + next(27))
                / (double)(1L << 54);}

This might seem to be equivalent, if not better, but in fact it introduced a large nonuniformity because of the bias in the rounding of floating-point numbers: it was three times as likely that the low-order bit of the significand would be 0 than that it would be 1! This nonuniformity probably doesn't matter much in practice, but we strive for perfection.]

Java documentation for java.util.Random.nextDouble().

Portions of this page are modifications based on work created and shared by the Android Open Source Project and used according to terms described in the Creative Commons 2.5 Attribution License.

Applies to