Java SecureRandom getInstance()方法及示例

getInstance( String algorithm )

java.security.SecureRandom 类的 getInstance() 方法用于返回一个实现了指定的随机数发生器（RNG）算法的SecureRandom对象。

这个方法会遍历已注册的安全提供商的列表，从最喜欢的提供商开始。一个新的SecureRandom对象封装了来自第一个支持指定算法的提供者的SecureRandomSpi实现，并被返回。

语法

public static SecureRandom getInstance( String algorithm ) throws NoSuchAlgorithmException

参数： 该方法接受 标准RNG算法 作为参数。

返回值： 该方法返回新的 SecureRandom 对象。

异常： 该方法抛出 NoSuchAlgorithmException - 如果没有提供商支持指定算法的SecureRandomSpi实现。

注意

这些程序将不会在在线IDE上运行。每次安全随机类都会产生随机输出:

下面是说明 getInstance() 方法的例子。

例子1 :

// Java program to demonstrate// nextBytes() method  import java.security.*;import java.util.*;  public class GFG1 {    public static void main(String[] argv)    {        try {            // creating the object of SecureRandom and getting instance            // By using getInstance() method            SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");              // 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

Byte array before operation : [84, 97, 106, 109, 97, 104, 97, 108]Byte array after operation : [124, -66, -62, -5, -71, -4, 30, 16]

例2 :

// Java program to demonstrate// getInstance() method  import java.security.*;import java.util.*;  public class GFG1 {    public static void main(String[] argv)    {        try {            // creating the object of SecureRandom and getting instance            // By using getInstance() method            System.out.println("Trying to get the instance of TAJMAHAL");            SecureRandom sr = SecureRandom.getInstance("TAJMAHAL");              // 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

Trying to get the instance of TAJMAHALException thrown : java.security.NoSuchAlgorithmException: TAJMAHAL SecureRandom not available

getInstance(String algorithm, Provider provider)

java.security.SecureRandom 类的 getInstance() 方法用于返回一个实现了指定的随机数发生器（RNG）算法的SecureRandom对象。
一个新的SecureRandom对象封装了来自指定的提供者对象的SecureRandomSpi实现，被返回。请注意，指定的提供者对象不需要在提供者列表中注册。

返回的SecureRandom对象还没有被播种。要对返回的对象进行播种，请调用setSeed方法。如果不调用setSeed，对nextBytes的第一次调用将强制SecureRandom对象进行自我播种。如果之前调用了setSeed，这种自我播种将不会发生。

语法

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

参数： 该方法接受以下参数作为参数

返回值： 该方法返回 新的SecureRandom对象

异常： 该方法会抛出以下异常

注意

这些程序将不会在在线IDE上运行。每次安全随机类都会产生随机输出:

下面是说明getInstance()方法的例子。

例1:

// 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

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： 下面的程序在在线IDE中产生了如下异常
抛出的异常：java.security.ProviderException: init failed

例2:

// 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

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

getInstance(String algorithm, String provider)

java.security.SecureRandom 类的 getInstance() 方法用于返回一个实现了指定的随机数发生器（RNG）算法的SecureRandom对象。

一个新的SecureRandom对象封装了来自指定提供者的SecureRandomSpi实现，并被返回。指定的提供者必须在安全提供者列表中注册。

语法

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

参数： 该方法接受以下参数作为参数

返回值： 该方法返回 新的SecureRandom对象

异常： 该方法会抛出以下异常

注意。

这些程序将不会在在线IDE上运行。每次安全随机类都会产生随机输出:

下面是说明getInstance()方法的例子。

例1:

// 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

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 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

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

例3:

// 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

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