Generating Password and OTP in Java

28 Jun, 2022
You may go through Generate a One Time Password or Unique Identification URL article before this for better understanding.  
Many a times we forget our passwords and we opt for Forget password option and within no time we get a new password at our registered email-ID or phone no. to login our account. And every time we get a different password. Sometimes we access our bank accounts while shopping from an online store or many more ways, in order to verify our transactions from the bank account, they send us OTP(One Time Password) on our registered phone no. or our email-ID, within no time. The following code explains how to generate such Passwords and OTP within no time and what code we can use if in case we need to do so.
Method 1:
Java program explaining the generation of Password 
Java
// Java code to explain how to generate random// password  // Here we are using random() method of util// class in Javaimport java.util.*;  public class NewClass{    public static void main(String[] args)    {        // Length of your password as I have choose        // here to be 8        int length = 10;        System.out.println(geek_Password(length));    }      // This our Password generating method    // We have use static here, so that we not to    // make any object for it    static char[] geek_Password(int len)    {        System.out.println("Generating password using random() : ");        System.out.print("Your new password is : ");          // A strong password has Cap_chars, Lower_chars,        // numeric value and symbols. So we are using all of        // them to generate our password        String Capital_chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";        String Small_chars = "abcdefghijklmnopqrstuvwxyz";        String numbers = "0123456789";                String symbols = "!@#$%^&*_=+-/.?<>)";            String values = Capital_chars + Small_chars +                        numbers + symbols;          // Using random method        Random rndm_method = new Random();          char[] password = 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            password[i] =              values.charAt(rndm_method.nextInt(values.length()));          }        return password;    }}
Note : The password we are generating will change every time. As we have used random() method to generate the password. 
Output : 
Generating password using random() : 
Your new password is : KHeCZBTM;-
Java program explaining the generation of OTP(One Time Password)
Java
// Java code to explain how to generate OTP  // Here we are using random() method of util// class in Javaimport 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));    }}
Note : The OTP we are generating will change every time. As we have used random() method to generate the OTP. 
Output : 
Generating OTP using random() : 
You OTP is : 5291
Method 2:
Java program explaining the generation of Password 
Java
// Java code to explain how to generate random// passwordclass 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 characterpublic static void main(String args[]) {long code=Code();//function callingString 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
Note : The password we are generating will change every time. As we have used random() method to generate the password. 
Output : 
Generating password using Math.random() and ascii code: 
Your new password is : KHe%ZBT$
Java program explaining the generation of OTP(One Time Password)
Java
// Java code to explain how to generate OTPpublic class GenerateOTP {//declaring a of return type String//which on calling provides the otp    public static String generateOTP()     {  //int randomPin declared to store the otp        //since we using Math.random() hence we have to type cast it int        //because Math.random() returns decimal value        int randomPin   =(int) (Math.random()*9000)+1000;        String otp  = String.valueOf(randomPin);        return otp; //returning value of otp    }            public static void main(String args[])//method to call and print otp    {        String otpSting  =generateOTP();//function calling        System.out.println("OTP : "+otpSting);    }}// Here we are using Math.random() function.// class in Java
Note : The OTP we are generating will change every time. As we have used Math.random() function to generate the OTP. 
Output : 
Generating OTP using random() : 
You OTP is : 5291
This article is contributed by Mohit Gupta . If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
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