项目场景：

最近项目生成id懒得用Twitter那个雪花法了，寻思着弄时间戳随机字符串算了
发现个挺好的用的类
org.apache.commons.lang.RandomStringUtils;

 public static String random(int count, boolean letters, boolean numbers) {
        return random(count, 0, 0, letters, numbers);
    }

    public static String random(int count, int start, int end, boolean letters, boolean numbers) {
        return random(count, start, end, letters, numbers, (char[])null, RANDOM);
    }

    public static String random(int count, int start, int end, boolean letters, boolean numbers, char[] chars) {
        return random(count, start, end, letters, numbers, chars, RANDOM);
    }

里面有多种参数供你配置，生成想要的字符串

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解决方案：

例子：

String randStr = RandomStringUtils.random(7, true, true);