This file shows some examples how to generate string filled with random chars.

FillArrayWithRandomChars.java

import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.stream.IntStream;


public class Main {
    public static void main(String[] args) {
        java7Way();
        java8Way();
        java8AlphabetWay();
    }

    public static void java7Way() {
        char[] arr = new char[60];
        Random rand = new Random();
        for (int i = 0; i < 60; i++) {
            int r = rand.nextInt(136);
            if (r >= 65) {
                arr[i] = (char) r;
            } else i--;
        }
        System.out.println(arr);
    }

    public static void java8Way() {
        char[] arr = new char[60];
        List<Character> list = new ArrayList<>();
        new Random().ints(60, 65, 123).forEach(e -> list.add((char) e));
        IntStream.range(0, 60).forEach(e -> arr[e] = list.get(e));
        System.out.println(arr);
    }
    
    public static void java8AlphabetWay() {
        IntStream.range(0, 60).forEach(e -> System.out.print("абвгдеёжзийклмнопрстуфхцчшщъыьэюя".charAt(new Random(e).nextInt(33))));
    }
}