Is there functionality to generate a random character in Java?

Question

Does Java have any functionality to generate random characters or strings? Or must one simply pick a random integer and convert that integer\'s ascii code to a character?

Answer 1

Here is the code to generate random alphanumeric code. First you have to declare a string of allowed characters what you want to include in random number.and also define max length of string

 SecureRandom secureRandom = new SecureRandom();
 String CHARACTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ123456789";
    StringBuilder generatedString= new StringBuilder();
    for (int i = 0; i < MAXIMUM_LENGTH; i++) {
        int randonSequence = secureRandom .nextInt(CHARACTERS.length());
        generatedString.append(CHARACTERS.charAt(randonSequence));
    }

Use toString() method to get String from StringBuilder

Answer 2

Take a look at Java Randomizer class. I think you can randomize a character using the randomize(char[] array) method.

Answer 3

In fact mentioned methods don't generate real random char. To generate real random char you should give it a random seed! in example time in millisecond. this code generate 10 random char and then Convert it to String:

import java.util.Random;
public class MyClass {
    public static void main() {

     String randomKey;

    char[] tempArray={0,0,0,0,0,0,0,0,0,0};  //ten characters

    long seed=System.currentTimeMillis();
    Random random=new Random(seed);
    for (int aux=0; aux<10;aux++){

        tempArray[aux]=(char) random.nextInt(255);
        System.out.println(tempArray[aux]);
    }

    randomKey=String.copyValueOf(tempArray);  


      System.out.println(randomKey);
    }
}

Answer 4

There are many ways to do this, but yes, it involves generating a random int (using e.g. java.util.Random.nextInt) and then using that to map to a char. If you have a specific alphabet, then something like this is nifty:

    import java.util.Random;

    //...

    Random r = new Random();

    String alphabet = "123xyz";
    for (int i = 0; i < 50; i++) {
        System.out.println(alphabet.charAt(r.nextInt(alphabet.length())));
    } // prints 50 random characters from alphabet

---

Do note that java.util.Random is actually a pseudo-random number generator based on the rather weak linear congruence formula. You mentioned the need for cryptography; you may want to investigate the use of a much stronger cryptographically secure pseudorandom number generator in that case (e.g. java.security.SecureRandom).

Answer 5

If you don't mind adding a new library in your code you can generate characters with MockNeat (disclaimer: I am one of the authors).

MockNeat mock = MockNeat.threadLocal();

Character chr = mock.chars().val();
Character lowerLetter = mock.chars().lowerLetters().val();
Character upperLetter = mock.chars().upperLetters().val();
Character digit = mock.chars().digits().val();
Character hex = mock.chars().hex().val(); 

Answer 6

public static void  main(String[] args) {

  //  System.out.println("Enter a number to changeit at char  ");
    Random random = new Random();

    int x = random.nextInt(26)+65;    //0  to 25
    System.out.println((char)x);
}