Generating Password and OTP in Java

        // Java code to explain how to generate OTP 
  
// Here we are using random() method of util 
// class in Java 
import java.util.*; 
  
public class NewClass 
{ 
    static char[] OTP(int len) 
    { 
        System.out.println("Generating OTP using random() : "); 
        System.out.print("You OTP is : "); 
  
        // Using numeric values 
        String numbers = "0123456789"; 
  
        // Using random method 
        Random rndm_method = new Random(); 
  
        char[] otp = new char[len]; 
  
        for (int i = 0; i < len; i++) 
        { 
            // Use of charAt() method : to get character value 
            // Use of nextInt() as it is scanning the value as int 
            otp[i] = 
             numbers.charAt(rndm_method.nextInt(numbers.length())); 
        } 
        return otp; 
    } 
    public static void main(String[] args) 
    { 
        int length = 4; 
        System.out.println(OTP(length)); 
    } 
} 
      

        // Java code to explain how to generate random 
// password 
class uniquePassword 
{ 
public static long Code() //this code returns the  unique 16 digit code  
{  //creating a 16 digit code using Math.random function 
    long code   =(long)((Math.random()*9*Math.pow(10,15))+Math.pow(10,15)); 
    return code; //returning the code 
} 
    //method to generate the password 
    //by converting every two digits as an ascii value of a character 
public static void main(String args[])  
{ 
long code=Code();//function calling 
String unique_password=""; 
for (long i=code;i!=0;i/=100)//a loop extracting 2 digits from the code  
    { 
        long digit=i%100;//extracting two digits 
        if (digit<=90) 
        digit=digit+32;  
        //converting those two digits(ascii value) to its character value 
        char ch=(char) digit; 
        // adding 32 so that our least value be a valid character  
        unique_password=ch+unique_password;//adding the character to the string 
    } 
    System.out.println("unique password ="+unique_password); 
    } 
} 
// Here we are using random() method of util 
// class in Java