Java 中 SecureRandom setSeed()方法,带示例

原文:https://www . geesforgeks . org/secureandom-setseed-method-in-Java-with-examples/

setSeed( byte[] seed )

Java . security . secureandom类的 setSeed() 方法用于重新播种这个随机对象。给定的种子补充而不是取代现有的种子。因此,重复调用保证永远不会降低随机性。

语法:

public void setSeed(byte[] seed)

参数:该方法以种子为参数。

注意:每次安全随机类都会产生随机输出

以下是说明设置种子()方法的示例:

例 1:

// Java program to demonstrate
// setSeed() method

import java.security.*;
import java.util.*;

public class GFG1 {
    public static void main(String[] argv)
    {
        try {
            // creating the object of SecureRandom
            SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");

            // Declaring the string variable
            String str = "Tajmahal";

            // Declaring the byte Array b
            byte[] b = str.getBytes();

            // Reseeding the random object
            sr.setSeed(b);

            // getting the seeds
            byte[] seeds = sr.getSeed(10);

            // printing the seed serialwise
            for (int i = 0; i < seeds.length; i++)
                System.out.println("Seed[" + i + "] : " + seeds[i]);
        }

        catch (NoSuchAlgorithmException e) {

            System.out.println("Exception thrown : " + e);
        }

        catch (ProviderException e) {

            System.out.println("Exception thrown : " + e);
        }
    }
}

输出:

Seed[0]:69
Seed[0] : 23
Seed[1] : -99
Seed[2] : -51
Seed[3] : 107
Seed[4] : 41
Seed[5] : -96
Seed[6] : -93
Seed[7] : -86
Seed[8] : 127
Seed[9] : 47

例 2:

// Java program to demonstrate
// setSeed() method

import java.security.*;
import java.util.*;

public class GFG1 {
    public static void main(String[] argv)
    {
        try {
            // creating the object of SecureRandom
            SecureRandom sr = new SecureRandom(new byte[] { 1, 2, 3, 4 });

            // Declaring the string variable
            String str = "Tajmahal";

            // Declaring the byte Array b
            byte[] b = str.getBytes();

            // Reseeding the random object
            sr.setSeed(b);

            // getting the seeds
            byte[] seeds = sr.getSeed(10);

            // printing the seed serialwise
            for (int i = 0; i < seeds.length; i++)
                System.out.println("Seed[" + i + "]:" + seeds[i]);
        }

        catch (ProviderException e) {

            System.out.println("Exception thrown : " + e);
        }
    }
}

输出:

Seed[0]:92
Seed[1]:127
Seed[2]:28
Seed[3]:-127
Seed[4]:-100
Seed[5]:-110
Seed[6]:86
Seed[7]:-55
Seed[8]:48
Seed[9]:-78

setSeed(long seed)

Java . security . secureandom类的 setSeed(长种子)方法用于使用给定长种子中包含的八个字节重新播种这个随机对象。给定的种子补充而不是取代现有的种子。因此,重复调用保证永远不会降低随机性。

语法:

public void setSeed( long seed )

参数:该方法以种子为参数

注意:每次安全随机类都会产生随机输出

以下是说明设置种子()方法的示例:

例 1:

// Java program to demonstrate
// setSeed() method

import java.security.*;
import java.util.*;

public class GFG1 {
    public static void main(String[] argv) throws Exception
    {
        try {
            // creating the object of SecureRandom
            SecureRandom sr = SecureRandom.getInstance("SHA1PRNG", "SUN");

            // Reseeding the random object
            sr.setSeed(101L);

            // getting the seeds
            byte[] seeds = sr.getSeed(10);

            // printing the seed serialwise
            for (int i = 0; i < seeds.length; i++)
                System.out.println("Seed[" + i + "] : " + seeds[i]);
        }

        catch (NoSuchAlgorithmException e) {

            System.out.println("Exception thrown : " + e);
        }

        catch (ProviderException e) {

            System.out.println("Exception thrown : " + e);
        }
    }
}

输出:

Seed[0] : -36
Seed[1] : -65
Seed[2] : -94
Seed[3] : 16
Seed[4] : -104

例 2:

// Java program to demonstrate
// setSeed() method

import java.security.*;
import java.util.*;

public class GFG1 {
    public static void main(String[] argv)
    {
        try {
            // creating the object of SecureRandom
            SecureRandom sr = new SecureRandom(new byte[] { 1, 2, 3, 4 });

            // Reseeding the random object
            sr.setSeed(101L);

            // getting the seeds
            byte[] seeds = sr.getSeed(10);

            // printing the seed serialwise
            for (int i = 0; i < seeds.length; i++)
                System.out.println("Seed[" + i + "]:" + seeds[i]);
        }

        catch (ProviderException e) {

            System.out.println("Exception thrown : " + e);
        }
    }
}

输出:

Seed[0]:-29
Seed[1]:-93
Seed[2]:6
Seed[3]:66
Seed[4]:126
Seed[5]:93
Seed[6]:-58
Seed[7]:-91
Seed[8]:-62
Seed[9]:-58