how to get a random value from an array to another in java

I want to get a random array value from char[] vowel and char[] consonant into char[] firstName and char[] lastName.

My IDE (Eclipse) shows no errors for

firstName[i]=consonant [random.nextInt(consonant.length)];

however when running the code i'll get the error

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0 at _01NameGenerator.main(_01NameGenerator.java:27)

How shall I fix this statement?

import java.util.Random;

public class _01NameGenerator {

    public static void main(String[] args) {
        Random random = new Random();
        int nameMinimum = 3;
        int nameRange = 7;
        int firstNameLength = nameMinimum + (int) (Math.random()* nameRange); //nameRange suits better than nameMaximum
        int lastNameLength = nameMinimum + (int) (Math.random()* nameRange);  

        System.out.println("Your firstname will be "+firstNameLength+" and you lastname "+lastNameLength+" characters long.");

        char[] vowel = {'a', 'e', 'i', 'o', 'u', 'y'};      
        char[] consonant = {'b', 'c', 'd', 'f', 'g', 'h', 'j', 'k', 'l', 'm', 'n', 'p', 'q', 'r', 's', 't', 'v', 'w', 'x', 'z'};

        char[] firstName = {};
        char[] lastName = {};

        boolean wechsel = true;

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

            if (wechsel == true){

                firstName[i]=consonant [random.nextInt(consonant.length)];
                wechsel = false;

            } else {

                firstName[i]=vowel [random.nextInt(vowel.length)];
                wechsel = true;
            }

        }   

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

            if (wechsel == true){

                lastName[i]=consonant [random.nextInt(consonant.length)];
                wechsel = false;

            } else {

                lastName[i]=vowel [random.nextInt(vowel.length)];
                wechsel = true;
            }

        }   

        System.out.println(firstName + "" + lastName);

    }

}