极客教程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 TAJMAHAL
Exception 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
- algorithm – RNG算法的名称。
- provider – 提供者。
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
- NoSuchAlgorithmException – 如果指定算法的SecureRandomSpi实现在指定的提供者对象中不可用。
- IllegalArgumentException – 如果指定的提供者为空。
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 TAJMAHAL
Exception 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
- algorithm – RNG算法的名称。关于标准RNG算法名称的信息，请参见Java Cryptography Architecture Standard Algorithm Name Documentation中的SecureRandom部分。
- provider – 提供者的名称。
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
- NoSuchAlgorithmException – 如果指定算法的SecureRandomSpi实现无法从指定的提供者那里获得。
- NoSuchProviderException – 如果指定的提供者没有在安全提供者列表中注册。
- IllegalArgumentException – 如果提供者的名字是空的或空的。
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 algorithm
Exception 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 provider
Exception thrown : java.security.NoSuchProviderException: no such provider: MOON