public static String randomStringFixLength(int length) {
		return RandomStringUtils.random(length, 0, 0, true, true, null, threadLocalRandom());
	}
public static String randomStringFixLength ( int length ) { return RandomStringUtils . random ( length , 0 , 0 , true , true , null , threadLocalRandom ( ) ) ; }
随机字母或数字，固定长度