Random.NextDouble 方法
定義
重要
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回傳一個大於或等於 0.0 且小於 1.0 的隨機浮點數。
public:
virtual double NextDouble();public virtual double NextDouble();abstract member NextDouble : unit -> double
override this.NextDouble : unit -> doublePublic Overridable Function NextDouble () As Double傳回
一個大於或等於0.0且小於1.0的雙精度浮點數。
範例
以下範例使用此 NextDouble 方法生成隨機雙重序列。
// Example of the Random class constructors and Random.NextDouble()
// method.
using System;
using System.Threading;
public class RandomObjectDemo
{
// Generate random numbers from the specified Random object.
static void RunIntNDoubleRandoms(Random randObj)
{
// Generate the first six random integers.
for(int j = 0; j < 6; j++)
Console.Write(" {0,10} ", randObj.Next());
Console.WriteLine();
// Generate the first six random doubles.
for(int j = 0; j < 6; j++)
Console.Write(" {0:F8} ", randObj.NextDouble());
Console.WriteLine();
}
// Create a Random object with the specified seed.
static void FixedSeedRandoms(int seed)
{
Console.WriteLine(
"\nRandom numbers from a Random object with " +
"seed = {0}:", seed);
Random fixRand = new Random(seed);
RunIntNDoubleRandoms(fixRand);
}
// Create a random object with a timer-generated seed.
static void AutoSeedRandoms()
{
// Wait to allow the timer to advance.
Thread.Sleep(1);
Console.WriteLine(
"\nRandom numbers from a Random object " +
"with an auto-generated seed:");
Random autoRand = new Random();
RunIntNDoubleRandoms(autoRand);
}
static void Main()
{
Console.WriteLine(
"This example of the Random class constructors and " +
"Random.NextDouble() \n" +
"generates the following output.\n");
Console.WriteLine(
"Create Random objects, and then generate and " +
"display six integers and \nsix doubles from each.");
FixedSeedRandoms(123);
FixedSeedRandoms(123);
FixedSeedRandoms(456);
FixedSeedRandoms(456);
AutoSeedRandoms();
AutoSeedRandoms();
AutoSeedRandoms();
}
}
/*
This example of the Random class constructors and Random.NextDouble()
generates an output similar to the following:
Create Random objects, and then generate and display six integers and
six doubles from each.
Random numbers from a Random object with seed = 123:
2114319875 1949518561 1596751841 1742987178 1586516133 103755708
0.01700087 0.14935942 0.19470390 0.63008947 0.90976122 0.49519146
Random numbers from a Random object with seed = 123:
2114319875 1949518561 1596751841 1742987178 1586516133 103755708
0.01700087 0.14935942 0.19470390 0.63008947 0.90976122 0.49519146
Random numbers from a Random object with seed = 456:
2044805024 1323311594 1087799997 1907260840 179380355 120870348
0.21988117 0.21026556 0.39236514 0.42420498 0.24102703 0.47310170
Random numbers from a Random object with seed = 456:
2044805024 1323311594 1087799997 1907260840 179380355 120870348
0.21988117 0.21026556 0.39236514 0.42420498 0.24102703 0.47310170
Random numbers from a Random object with an auto-generated seed:
380213349 127379247 1969091178 1983029819 1963098450 1648433124
0.08824121 0.41249688 0.36445811 0.05637512 0.62702451 0.49595560
Random numbers from a Random object with an auto-generated seed:
861793304 2133528783 1947358439 124230908 921262645 1087892791
0.56880819 0.42934091 0.60162512 0.74388610 0.99432979 0.30310005
Random numbers from a Random object with an auto-generated seed:
1343373259 1992194672 1925625700 412915644 2026910487 527352458
0.04937517 0.44618494 0.83879212 0.43139707 0.36163507 0.11024451
*/
// Example of the Random class constructors and Random.NextDouble()
// method.
open System
open System.Threading
// Generate random numbers from the specified Random object.
let runIntNDoubleRandoms (randObj: Random) =
// Generate the first six random integers.
for _ = 1 to 6 do
printf $" {randObj.Next(),10} "
printfn ""
// Generate the first six random doubles.
for _ = 1 to 6 do
printf $" {randObj.NextDouble():F8} "
printfn ""
let fixedSeedRandoms seed =
printfn $"\nRandom numbers from a Random object with seed = %i{seed}:"
let fixRand = Random seed
runIntNDoubleRandoms fixRand
let autoSeedRandoms () =
// Wait to allow the timer to advance.
Thread.Sleep 1
printfn "\nRandom numbers from a Random object with an auto-generated seed: "
let autoRand = Random ()
runIntNDoubleRandoms autoRand
printfn
"""This example of the Random class constructors and Random.NextDouble()
generates the following output.
Create Random objects, and then generate and display six integers and
six doubles from each."""
fixedSeedRandoms 123
fixedSeedRandoms 123
fixedSeedRandoms 456
fixedSeedRandoms 456
autoSeedRandoms ()
autoSeedRandoms ()
autoSeedRandoms ()
(*
This example of the Random class constructors and Random.NextDouble()
generates an output similar to the following:
Create Random objects, and then generate and display six integers and
six doubles from each.
Random numbers from a Random object with seed = 123:
2114319875 1949518561 1596751841 1742987178 1586516133 103755708
0.01700087 0.14935942 0.19470390 0.63008947 0.90976122 0.49519146
Random numbers from a Random object with seed = 123:
2114319875 1949518561 1596751841 1742987178 1586516133 103755708
0.01700087 0.14935942 0.19470390 0.63008947 0.90976122 0.49519146
Random numbers from a Random object with seed = 456:
2044805024 1323311594 1087799997 1907260840 179380355 120870348
0.21988117 0.21026556 0.39236514 0.42420498 0.24102703 0.47310170
Random numbers from a Random object with seed = 456:
2044805024 1323311594 1087799997 1907260840 179380355 120870348
0.21988117 0.21026556 0.39236514 0.42420498 0.24102703 0.47310170
Random numbers from a Random object with an auto-generated seed:
380213349 127379247 1969091178 1983029819 1963098450 1648433124
0.08824121 0.41249688 0.36445811 0.05637512 0.62702451 0.49595560
Random numbers from a Random object with an auto-generated seed:
861793304 2133528783 1947358439 124230908 921262645 1087892791
0.56880819 0.42934091 0.60162512 0.74388610 0.99432979 0.30310005
Random numbers from a Random object with an auto-generated seed:
1343373259 1992194672 1925625700 412915644 2026910487 527352458
0.04937517 0.44618494 0.83879212 0.43139707 0.36163507 0.11024451
*)
' Example of the Random class constructors and Random.NextDouble()
' method.
Imports System.Threading
Module RandomObjectDemo
' Generate random numbers from the specified Random object.
Sub RunIntNDoubleRandoms(randObj As Random)
' Generate the first six random integers.
Dim j As Integer
For j = 0 To 5
Console.Write(" {0,10} ", randObj.Next())
Next j
Console.WriteLine()
' Generate the first six random doubles.
For j = 0 To 5
Console.Write(" {0:F8} ", randObj.NextDouble())
Next j
Console.WriteLine()
End Sub
' Create a Random object with the specified seed.
Sub FixedSeedRandoms(seed As Integer)
Console.WriteLine(vbCrLf & _
"Random numbers from a Random object with " & _
"seed = {0}:", seed)
Dim fixRand As New Random(seed)
RunIntNDoubleRandoms(fixRand)
End Sub
' Create a random object with a timer-generated seed.
Sub AutoSeedRandoms()
' Wait to allow the timer to advance.
Thread.Sleep(1)
Console.WriteLine(vbCrLf & _
"Random numbers from a Random object " & _
"with an auto-generated seed:")
Dim autoRand As New Random()
RunIntNDoubleRandoms(autoRand)
End Sub
Sub Main()
Console.WriteLine(_
"This example of the Random class constructors " & _
"and Random.NextDouble() " & vbCrLf & _
"generates the following output." & vbCrLf)
Console.WriteLine("Create Random " & _
"objects, and then generate and display six " & _
"integers and " & vbCrLf & "six doubles from each.")
FixedSeedRandoms(123)
FixedSeedRandoms(123)
FixedSeedRandoms(456)
FixedSeedRandoms(456)
AutoSeedRandoms()
AutoSeedRandoms()
AutoSeedRandoms()
End Sub
End Module
' This example of the Random class constructors and Random.NextDouble()
' generates an output similar to the following:
'
' Create Random objects, and then generate and display six integers and
' six doubles from each.
'
' Random numbers from a Random object with seed = 123:
' 2114319875 1949518561 1596751841 1742987178 1586516133 103755708
' 0.01700087 0.14935942 0.19470390 0.63008947 0.90976122 0.49519146
'
' Random numbers from a Random object with seed = 123:
' 2114319875 1949518561 1596751841 1742987178 1586516133 103755708
' 0.01700087 0.14935942 0.19470390 0.63008947 0.90976122 0.49519146
'
' Random numbers from a Random object with seed = 456:
' 2044805024 1323311594 1087799997 1907260840 179380355 120870348
' 0.21988117 0.21026556 0.39236514 0.42420498 0.24102703 0.47310170
'
' Random numbers from a Random object with seed = 456:
' 2044805024 1323311594 1087799997 1907260840 179380355 120870348
' 0.21988117 0.21026556 0.39236514 0.42420498 0.24102703 0.47310170
'
' Random numbers from a Random object with an auto-generated seed:
' 1920831619 1346865774 2006582766 1968819760 332463652 110770792
' 0.71326689 0.50383335 0.50446082 0.66312569 0.94517193 0.58059287
'
' Random numbers from a Random object with an auto-generated seed:
' 254927927 1205531663 1984850027 110020849 1438111494 1697714106
' 0.19383387 0.52067738 0.74162783 0.35063667 0.31247720 0.38773733
'
' Random numbers from a Random object with an auto-generated seed:
' 736507882 1064197552 1963117288 398705585 396275689 1137173773
' 0.67440084 0.53752140 0.97879483 0.03814764 0.67978248 0.19488178
以下範例呼叫 NextDouble 生成 100 個隨機數的方法，並顯示其頻率分布。
int[] frequency = new int[10];
double number;
Random rnd = new Random();
for (int ctr = 0; ctr <= 99; ctr++) {
number = rnd.NextDouble();
frequency[(int) Math.Floor(number*10)] ++;
}
Console.WriteLine("Distribution of Random Numbers:");
for (int ctr = frequency.GetLowerBound(0); ctr <= frequency.GetUpperBound(0); ctr++)
Console.WriteLine("0.{0}0-0.{0}9 {1}", ctr, frequency[ctr]);
// The following example displays output similar to the following:
// Distribution of Random Numbers:
// 0.00-0.09 16
// 0.10-0.19 8
// 0.20-0.29 8
// 0.30-0.39 11
// 0.40-0.49 9
// 0.50-0.59 6
// 0.60-0.69 13
// 0.70-0.79 6
// 0.80-0.89 9
// 0.90-0.99 14
let rnd = Random()
let frequency =
Array.init 100 (fun _ ->
let number = rnd.NextDouble()
floor (number * 10.0) |> int )
|> Array.countBy id
|> Array.map snd
printfn "Distribution of Random Numbers:"
for i = frequency.GetLowerBound 0 to frequency.GetUpperBound 0 do
printfn $"0.{i}0-0.{i}9 {frequency.[i]}"
// The following example displays output similar to the following:
// Distribution of Random Numbers:
// 0.00-0.09 16
// 0.10-0.19 8
// 0.20-0.29 8
// 0.30-0.39 11
// 0.40-0.49 9
// 0.50-0.59 6
// 0.60-0.69 13
// 0.70-0.79 6
// 0.80-0.89 9
// 0.90-0.99 14
Module Example
Public Sub Main()
Dim frequency(9) As Integer
Dim number As Double
Dim rnd As New Random()
For ctr As Integer = 0 To 99
number = rnd.NextDouble()
frequency(CInt(Math.Floor(number*10))) += 1
Next
Console.WriteLine("Distribution of Random Numbers:")
For ctr As Integer = frequency.GetLowerBound(0) To frequency.GetUpperBound(0)
Console.WriteLine("0.{0}0-0.{0}9 {1}", ctr, frequency(ctr))
Next
End Sub
End Module
' The following example displays output similar to the following:
' Distribution of Random Numbers:
' 0.00-0.09 16
' 0.10-0.19 8
' 0.20-0.29 8
' 0.30-0.39 11
' 0.40-0.49 9
' 0.50-0.59 6
' 0.60-0.69 13
' 0.70-0.79 6
' 0.80-0.89 9
' 0.90-0.99 14
備註
此方法回傳的隨機數實際上界為 0.99999999999999978。
若要取得除 0.0 和 1.0 以外的隨機浮點數值，請參閱類別主題中的 Random 「在指定範圍內取得浮點數值」章節。
此方法是受保護方法的公開版本。 Sample
