jodd-core/src/main/java/jodd/util/RandomString.java
public String random(int count, final char[] chars) {
		if (count == 0) {
			return StringPool.EMPTY;
		}
		final char[] result = new char[count];
		while (count-- > 0) {
			result[count] = chars[rnd.nextInt(chars.length)];
		}
		return new String(result);
	}
public String random(int count, final char[] chars) {
		if (count == 0) {
			return StringPool.EMPTY;
		}
		final char[] result = new char[count];
		while (count-- > 0) {
			result[count] = chars[rnd.nextInt(chars.length)];
		}
		return new String(result);
	}
Creates random string whose length is the number of characters specified.
Characters are chosen from the set of characters specified.