Java - generate random char array of size 10

public static char[] randomCharArray(int len) {

    String alphabet =

            "ABCDEFGHIJKLMNOPQRSTUVWXYZ" +

            "abcdefghijklmnopqrstuvwxyz" +

            "0123456789";

​

    StringBuilder b = new StringBuilder();

​

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

        int randIdx = new Random().nextInt(alphabet.length());

        char randChar = alphabet.charAt(randIdx);

        b.append(randChar);

    }

​

    return b.toString().toCharArray();

}

// [v, K, 5, f, H, R, k, j, O, K]

System.out.println(Arrays.toString(randomCharArray(10)));

​

// [h, U, x, V, u, P, C, c, 1, I]

System.out.println(Arrays.toString(randomCharArray(10)));

​

// [F, Z, p, i, 0, d, O, X, a, B]

System.out.println(Arrays.toString(randomCharArray(10)));