Java SecureRandom nextBytes()方法及示例

java.security.SecureRandom 类的 nextBytes() 方法是用来生成用户指定数量的随机字节的。

如果之前没有调用setSeed，对这个方法的第一次调用会迫使这个SecureRandom对象进行自我播种。如果之前调用了setSeed，这种自我播种就不会发生。

语法

public void nextBytes(byte[] bytes)

参数： 该方法以待填入随机字节的数组为参数。

注意

这些程序将不会在在线IDE上运行。每次Secure Random类都会产生随机输出:

下面是说明NextBytes()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            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 : [-79, -110, -18, -31, -54, -36, 63, -61]

注意： 以下程序在GeeksForGeeks IDE上会出现以下异常，但在任何命令提示符（JDK）上都能有效运行。

Exception thrown : java.security.ProviderException: init failed

例2 :

// 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            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();              // 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 (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 : [-14, 77, 123, 121, 116, 50, -89, -86]