public final class DefaultRandomStringGenerator
  implements RandomStringGenerator
{
  private static final char[] PRINTABLE_CHARACTERS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012345679".toCharArray();
  private static final int DEFAULT_MAX_RANDOM_LENGTH = 35;
  private SecureRandom randomizer = new SecureRandom();
  private final int maximumRandomLength;
  
  public DefaultRandomStringGenerator()
  {
    this.maximumRandomLength = 35;
  }
  
  public DefaultRandomStringGenerator(int maxRandomLength)
  {
    this.maximumRandomLength = maxRandomLength;
  }
  
  public int getMinLength()
  {
    return this.maximumRandomLength;
  }
  
  public int getMaxLength()
  {
    return this.maximumRandomLength;
  }
  
  public String getNewString()
  {
    byte[] random = getNewStringAsBytes();
    
    return convertBytesToString(random);
  }
  
  public byte[] getNewStringAsBytes()
  {
    byte[] random = new byte[this.maximumRandomLength];
    
    this.randomizer.nextBytes(random);
    
    return random;
  }
  
  private String convertBytesToString(byte[] random)
  {
    char[] output = new char[random.length];
    for (int i = 0; i < random.length; i++)
    {
      int index = Math.abs(random[i] % PRINTABLE_CHARACTERS.length);
      output[i] = PRINTABLE_CHARACTERS[index];
    }
    return new String(output);
  }

}

public abstract interface RandomStringGenerator
{
  public abstract int getMinLength();
  
  public abstract int getMaxLength();
  
  public abstract String getNewString();
  
  public abstract byte[] getNewStringAsBytes();

}