Java中的SecureRandomgetInstance()方法，带示例

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

字符串算法

Java . security . SecureRandom类的 getInstance() 方法用于返回实现指定随机数生成器(RNG)算法的 secureandom 对象。

此方法遍历注册的安全提供程序列表，从最首选的提供程序开始。返回一个新的安全对象，该对象封装了来自第一个支持指定算法的提供程序的安全对象。

语法:

参数:该方法以标准 RNG 算法为参数。

返回值:这个方法返回新的 SecureRandom 对象。

异常:如果没有提供程序支持指定算法的 SecureRandomSpi 实现，此方法将引发nosuchalgorithm 异常。

注:

1. 这些程序不会在联机集成开发环境中运行。


2. 每次安全随机类都会产生随机输出。

以下是说明 getInstance() 方法的示例:

例 1:

输出:

例 2:

输出:

getInstance(字符串算法，提供程序提供程序)

Java . security . SecureRandom类的 getInstance() 方法用于返回实现指定随机数生成器(RNG)算法的 secureandom 对象。
返回一个新的安全对象，该对象封装了来自指定提供程序对象的安全对象接口实现。请注意，指定的提供程序对象不必在提供程序列表中注册。

返回的安全对象尚未植入。若要为返回的对象设定种子，请调用 setSeed 方法。如果不调用 setSeed，对 nextBytes 的第一次调用将强制 SecureRandom 对象对自身进行种子化。如果之前调用了 setSeed，则不会发生这种自播种。

语法:

参数:该方法将以下参数作为参数

• 算法–RNG 算法的名称。


• 提供商–提供商。

返回值:该方法返回新的 SecureRandom 对象。

异常:该方法抛出以下异常

• no suchalgorithm exception–如果指定的提供程序对象中没有指定算法的 SecureRandomSpi 实现，则为。



• IllegalArgumentException – if the specified provider is null.

  注:

  
  
  1. 这些程序不会在联机集成开发环境中运行。
  
  
  2. 每次安全随机类都会产生随机输出。
  
  

  以下是说明 getInstance() 方法的示例:

  例 1:

  ```java
  // Java program to demonstrate
  // getInstance() method

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

  public class GFG1 {
      public static void main(String[] argv)
      {
          try {
              // creating SecureRandom object
              SecureRandom sr1 = new SecureRandom(new byte[] { 1, 2, 3, 4 });

  // creating Provider object
              Provider pd = sr1.getProvider();

  // creating the object of SecureRandom and getting instance
              // By using getInstance() method

  SecureRandom sr = SecureRandom.getInstance("SHA1PRNG", pd);

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

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

  // printing the byte array
              System.out.println("Byte array before operation : "
                                 + Arrays.toString(b));

  // generating user-specified number of random bytes
              // using nextBytes() method
              sr.nextBytes(b);

  // printing the new byte array
              System.out.println("Byte array after operation : "
                                 + Arrays.toString(b));
          }

  catch (NoSuchAlgorithmException e) {

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

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

  输出:

  java
Byte array before operation : [84, 97, 106, 109, 97, 104, 97, 108]
Byte array after operation : [109, 55, 116, -15, -83, 126, -128, 88]

  注意:以下程序在联机 IDE 中产生以下异常
  抛出异常:Java . security . providerexception:init 失败

  例 2:

  ```java
  // Java program to demonstrate
  // getInstance() method

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

  public class GFG1 {
      public static void main(String[] argv)
      {
          try {
              // creating SecureRandom object
              SecureRandom sr1 = new SecureRandom(new byte[] { 1, 2, 3, 4 });

  // creating Provider object
              Provider pd = sr1.getProvider();

  // creating the object of SecureRandom and getting instance
              // By using getInstance() method
              System.out.println("Trying to getting the instance of TAJMAHAL ");
              SecureRandom sr = SecureRandom.getInstance("TAJMAHAL", pd);

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

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

  // printing the byte array
              System.out.println("Byte array before operation : "
                                 + Arrays.toString(b));

  // generating user-specified number of random bytes
              // using nextBytes() method
              sr.nextBytes(b);

  // printing the new byte array
              System.out.println("Byte array after operation : "
                                 + Arrays.toString(b));
          }

  catch (NoSuchAlgorithmException e) {

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

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

  输出:

  java
Trying to getting the instance of TAJMAHAL
Exception thrown : java.security.NoSuchAlgorithmException: no such algorithm: TAJMAHAL for provider SUN

  getInstance(字符串算法，字符串提供程序)

  Java . security . SecureRandom类的 getInstance() 方法用于返回实现指定随机数生成器(RNG)算法的 secureandom 对象。

  返回一个新的安全对象，该对象封装了来自指定提供程序的安全对象接口实现。指定的提供程序必须在安全提供程序列表中注册。

  语法:

  java
public static SecureRandom
getInstance( String algorithm, String provider )
throws NoSuchAlgorithmException, NoSuchProviderException

  参数:该方法将以下参数作为参数

  
  
  • 算法–RNG 算法的名称。有关标准 RNG 算法名称的信息，请参见 Java 加密体系结构标准算法名称文档中的安全域部分。
  
  
  • 提供者–提供者的名称。
  
  

  返回值:该方法返回新的 SecureRandom 对象。

  异常:该方法抛出以下异常

  
  
  • no suchalgorithm exception–如果指定的提供程序无法提供指定算法的 SecureRandomSpi 实现。
  
  
  • NoSuchProviderException–如果指定的提供商未在安全提供商列表中注册。
  
  
  • IllegalArgumentException–如果提供程序名称为空。
  
  

  注:

  
  
  1. 这些程序不会在联机集成开发环境中运行。
  
  
  2. 每次安全随机类都会产生随机输出。
  
  

  以下是说明 getInstance() 方法的示例:

  例 1:

  ```java
  // Java program to demonstrate
  // getInstance() method

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

  public class GFG1 {
      public static void
          main(String[] argv)
              throws NoSuchAlgorithmException,
                     NoSuchProviderException
      {
          try {
              // creating SecureRandom object
              SecureRandom sr1 = new SecureRandom(new byte[] { 1, 2, 3, 4 });

  // creating Provider object
              Provider pd = sr1.getProvider();

  // getting provider name
              // by using method getname()
              String provider = pd.getName();

  // getting algorithm name
              // by using     getAlgorithm() mathod
              String algo = sr1.getAlgorithm();

  // creating the object of SecureRandom and getting instance
              // By using getInstance() method
              SecureRandom sr = SecureRandom.getInstance(algo, provider);

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

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

  // printing the byte array
              System.out.println("Byte array before operation : "
                                 + Arrays.toString(b));

  // generating user-specified number of random bytes
              // using nextBytes() method
              sr.nextBytes(b);

  // printing the new byte array
              System.out.println("Byte array after operation : "
                                 + Arrays.toString(b));
          }

  catch (NoSuchAlgorithmException e) {

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

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

  输出:

  java
Byte array before operation : [84, 97, 106, 109, 97, 104, 97, 108]
Byte array after operation : [-11, 81, 39, 67, -95, -51, 115, -18]

  例 2:

  ```java
  // Java program to demonstrate
  // getInstance() method

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

  public class GFG1 {
      public static void
          main(String[] argv)
              throws NoSuchAlgorithmException,
                     NoSuchProviderException
      {
          try {
              // creating SecureRandom object
              SecureRandom sr1 = new SecureRandom(new byte[] { 1, 2, 3, 4 });

  // creating Provider object
              Provider pd = sr1.getProvider();

  // getting provider name
              // by using method getname()
              String provider = pd.getName();

  // creating the object of SecureRandom and getting instance
              // By using getInstance() method
              System.out.println("Trying to take TAJMAHAL as a algorithm");
              SecureRandom sr = SecureRandom.getInstance("TAJMAHAL", provider);

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

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

  // printing the byte array
              System.out.println("Byte array before operation : "
                                 + Arrays.toString(b));

  // generating user-specified number of random bytes
              // using nextBytes() method
              sr.nextBytes(b);

  // printing the new byte array
              System.out.println("Byte array after operation : "
                                 + Arrays.toString(b));
          }

  catch (NoSuchAlgorithmException e) {

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

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

  输出:

  java
Trying to take TAJMAHAL as a algorithm
Exception thrown : java.security.NoSuchAlgorithmException: no such algorithm: TAJMAHAL for provider SUN

  例 3:

  ```java
  // Java program to demonstrate
  // getInstance() method

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

  public class GFG1 {
      public static void
          main(String[] argv)
              throws NoSuchAlgorithmException,
                     NoSuchProviderException
      {
          try {
              // creating SecureRandom object
              SecureRandom sr1 = new SecureRandom(new byte[] { 1, 2, 3, 4 });

  // getting algorithm name
              // by using     getAlgorithm() mathod
              String algo = sr1.getAlgorithm();

  // creating the object of SecureRandom and getting instance
              // By using getInstance() method
              System.out.println("Trying to taking MOON as a provider");
              SecureRandom sr = SecureRandom.getInstance(algo, "MOON");

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

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

  // printing the byte array
              System.out.println("Byte array before operation : "
                                 + Arrays.toString(b));

  // generating user-specified number of random bytes
              // using nextBytes() method
              sr.nextBytes(b);

  // printing the new byte array
              System.out.println("Byte array after operation : "
                                 + Arrays.toString(b));
          }

  catch (NoSuchAlgorithmException e) {

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

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

  输出:

  java
Trying to taking MOON as a provider
Exception thrown : java.security.NoSuchProviderException: no such provider: MOON