Random Java Programs: Random Password Generator

     Let us create a function which generates your password randomly. Let us see some formats of passwords.

Eg:

eR8!h0%kA*

how will it decide??

• ·       First, length of the password should be considered.
• ·       Next, uppercase, lowercase and numbers combination is needed.
• ·       Finally, the special characters are included.

Program implementation:

              It starts with the logic of the program.

Logic:

• ·       Get the length of the password from the user.
• ·       Call the function with password length.
• ·       Inside the function definition, assign uppercase, lowercase characters, numbers and special characters.
• ·       Combination of password is decided.
• ·       Using secureRandom class and stringBuilder, password is generated and displayed.

Let us implement this password generation program in java as follows.

·       First, include the built in packages.

·       Create a public class with main() function.

·       Create object for Scanner class which reads the system input.

·       Get the password length from user as integer.

·       Now, call the generatePwd() function with password length.

·       Function definition assigns uppercase,lowercase, numbers and special characters.

·       It also sets the combination of password.

·       Using secureRandom and stringBuilder classes, the password is generated randomly.

·       Finally, the password is displayed in the output screen.

Program:

//importing built-in packages

import java.security.SecureRandom;

import java.util.Scanner;

//Class with main() function

public class GeneratePassword {

    public static void main(String[] args) {

        //Getting the password length from the user

        Scanner s1 = new Scanner(System.in);

              System.out.println("Enter the password length");

        int pwdlen = s1.nextInt();

           //Call the generatePwd() function

        System.out.println("Generated Password: " + generatePwd(pwdlen));

    }

    //generatePwd() function definition

    public static String generatePwd(int length) {

        //Defining uppercase,lowercase,numbers and special characters

        String uCase = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

        String lCase = "abcdefghijklmnopqrstuvwxyz";

        String nos = "0123456789";

        String specialChars = "!@#$%^&*()-_=+[]{};:,.<>?";

        String allChars =  lCase + uCase + nos + specialChars;

        //Random password generation

        SecureRandom random1 = new SecureRandom();

        StringBuilder pwd = new StringBuilder();

        for (int i = 0; i < length; i++) {

            int index = random1.nextInt(allChars.length());

            pwd.append(allChars.charAt(index));

        }

        return pwd.toString();

    }

}

Output:

Compile and run the program to get the output as follows..

C:\raji\blog>javac GeneratePassword.java

C:\raji\blog>java GeneratePassword

Enter the password length

9

Generated Password: Uqv]ooeQ@

This is the way of creating random password generation program in java. Hope this code is useful to you. Keep coding!!!