Java Program to Create random Strings

In the following example of Java Program to Create random strings :

Program :

import java.util.Random;

public class RandomStringGenerator {
    public static void main(String[] args) {
        int length = 10; // The length of the random string
        String randomString = generateRandomString(length);
        System.out.println(randomString);
    }

    public static String generateRandomString(int length) {
        String characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
        Random random = new Random();
        StringBuilder sb = new StringBuilder(length);

        for (int i = 0; i < length; i++) {
            int index = random.nextInt(characters.length());
            sb.append(characters.charAt(index));
        }

        return sb.toString();
    }
}

Output :

IMyWI9Yh2V

In this program, we first specify the length of the random string that we want to generate. We then call the generateRandomString() method, which takes an integer argument length and returns a random string of length length.

The generateRandomString() method generates a random string by randomly selecting characters from a string containing all uppercase and lowercase letters and digits. It uses a Random object to generate random integers, which are used to select characters from the string. The StringBuilder class is used to construct the random string character by character.

Finally, the generateRandomString() method returns the constructed random string.

Example 2 : Java program to generate a random string (create a string of all characters) :

Program :

import java.util.Random;

class Main {
  public static void main(String[] args) {

    // create a string of all characters
    String alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    // create random string builder
    StringBuilder sb = new StringBuilder();

    // create an object of Random class
    Random random = new Random();

    // specify length of random string
    int length = 7;

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

      // generate random index number
      int index = random.nextInt(alphabet.length());

      // get character specified by index
      // from the string
      char randomChar = alphabet.charAt(index);

      // append the character to string builder
      sb.append(randomChar);
    }

    String randomString = sb.toString();
    System.out.println("Random String is: " + randomString);

  }
}

Output :

Random String is: IWPAJZJ

In the above example, we have first created a string containing all the alphabets. Next, we have generated a random index number using the nextInt() method of the Random class.

Using the random index number, we have generated the random character from the string alphabet. We then used the StringBuilder class to append all the characters together.

If we want to change the random string into lower case, we can use the toLowerCase() method of the String.