Introduction to Random () function usage in Java

Random ()

Creates a new random number generator.

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Random (Long Seed)

Creates a new random number generator with a single long seed.

We can specify the seed when constructing the random object, such as:

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Random r1 = new random (20);

or the default current system time for the number of times the http://www.111cn.net/jsp/Java/45403.htm should be relative to the number of seeds:

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Random r1 = new Random ();

The seed number is only the origin number of the stochastic algorithm, independent of the interval of the generated random numbers.

2. Common methods in random class

Here's a basic introduction to these methods:

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A, public boolean nextboolean ()

The function of this method is to generate a random Boolean value that generates a value of true and false that is equal to the probability of 50%.

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B, public double nextdouble ()

The function of this method is to generate a random double value between [0,1.0].

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c, public int nextint ()

The function of this method is to generate a random int value that is between the range of int, which is 231 to 231-1.

If you need to generate an int value for a specified interval, you need to make some mathematical transformations, as shown in the following example of using code.

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d, public int nextint (int n

)

The function of this method is to generate a random int value that is in the interval of [0,n], which is a random int value between 0 and N, containing 0 without n.

If you want to generate an int value for a specified interval, you also need to make some mathematical transformations, see the code in the example below.

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E, public void setseed (long Seed)

The function of this method is to reset the number of seeds in the random object. The random object and the same seed number after the seed number is set are created using the New keyword

The same as the random object.

3. Example of using the random class

Using the random class, which is usually generated by randomly generating a specified interval, describes how to generate random numbers for the corresponding interval. The following generates a random number of

The code is generated using the following random object R:

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Random r = new Random ();

A, the decimal number of the generation [0,1.0] Interval

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Double D1 = r.nextdouble ();

obtained directly using the Nextdouble method.

b, decimal for generating [0,5.0] Interval

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Double D2 = r.nextdouble () * 5;

Because the number interval generated by the Nextdouble method is [0,1.0], expanding the interval by 5 times times is the required interval.

Similarly, generating random decimals for the [0,d] interval, and d for any positive decimal, you only need to multiply the return value of the Nextdouble method by D.

c, the decimal number of the generation [1,2.5] Interval

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Double d3 = r.nextdouble () * 1.5 + 1;

To generate random decimals for the [1,2.5] interval, you only need to generate a random number for the [0,1.5] interval first, and then add 1 to the generated random number interval.

Similarly, generating random numbers (where D1 is not equal to 0) for any range of fractional ranges [D1,D2] that are not starting at 0, you only need to generate the [0,D2-D1] interval first.

Random numbers, then add D1 to the generated random number range.

d, generate any integer

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int n1 = R.nextint ();

You can use the Nextint method directly.

E, the integer that generates the [0,10] Interval

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int n2 = R.nextint (10); N2 = Math.Abs (r.nextint ()% 10);

The above two lines of code can generate an integer for the [0,10] Interval

Uniformity of distribution

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Import Java.util.Random; public class Randomdemo { /** * Boy Tribe * * @param args */ public static void Main (string[] args) { Random r = new Random (); int n5 = r.nextint (100); String ran = ""; if (N5 < 55) {//55-digit interval, 55% chance ran = "55%"; } else if (N5 < 95) {//[55,95), 40-digit interval, 40% chance ran = "40%"; } else { ran = "5%"; Residual odds, you know! } System.out.println (RAN); } }

Introduction to Random () function usage in Java