How to Generate Random Character in Java

1. Generate Random Character Using random.nextInt() in Java
2. Generate Random Character From a String Using random.nextInt() and charAt()
3. Generate Random Character Using RandomStringUtils of Apache Commons

In this tutorial, we will introduce how we can generate a random character using several methods. We will introduce three methods with examples to understand the topic better.

Generate Random Character Using random.nextInt() in Java

Random is the most commonly used class in Java to generate a random value, but it cannot generate characters. To randomize characters using the Random class, we can use random.nextInt() to generate random integers. Every character corresponds to a number.

We can use a character as a bound in the nextInt() function. In the following example, we can see that an object of the Random class is created and then (random.nextInt(26) + 'a') is used. Here, the character 'a' corresponds to the number 97, using which we can generate 26 random integers that correspond to the lower-case alphabet.

At last, we have to cast the generated integer to a char.

import java.util.Random;

public class RandomChar {
  public static void main(String[] args) {
    Random random = new Random();

    char randomizedCharacter = (char) (random.nextInt(26) + 'a');
    System.out.println("Generated Random Character: " + randomizedCharacter);
  }
}

Output:

Generated Random Character: p

Generate Random Character From a String Using random.nextInt() and charAt()

In the next example, we will again use the Random class, and its nextInt() method but generate a random character from an already defined set of characters.

Below we can see that setOfCharacters is a string with several characters, including alphabets, numbers, and symbols. To generate a random character from this string, we will use the length of setOfCharacters as the argument of random.nextInt(). Once a random integer is generated, we use it to get a character at a random index or position using charAt(). It will return a random char from setOfCharacters.

import java.util.Random;

public class RandomChar {
  public static void main(String[] args) {
    Random random = new Random();

    String setOfCharacters = "abcdefghxyz1234567-/@";

    int randomInt = random.nextInt(setOfCharacters.length());
    char randomChar = setOfCharacters.charAt(randomInt);

    System.out.println("Random character from string: " + randomChar);
  }
}

Output:

Random character from string: 4

Generate Random Character Using RandomStringUtils of Apache Commons

In the last example, we use a class RandomStringUtils from the Apache Commons library. RandomStringUtils class has a function randomAlphanumeric() to generate random alphanumeric strings. randomAlphanumeric(count) takes a single argument, that is the length of the randomized string that we want.

In the example below, we have passed only 1 to the randomAlphanumeric() method as we only want a single character. But this function returns the result as a string. This is why we have to convert it to a char. So, we use charAt() to get the character from the string.

import org.apache.commons.lang3.RandomStringUtils;

public class RandomChar {
  public static void main(String[] args) {
    String randomizedString = RandomStringUtils.randomAlphanumeric(1);
    char randomizedCharacter = randomizedString.charAt(0);

    System.out.println("Generated Random Character: " + randomizedCharacter);
  }
}

Output:

Generated Random Character: L