随机生成包含大小写特殊字符数字4种组成的密码

    
    public String setPassword(int len){
        char charr[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890~!@#$%^&*.?".toCharArray();
        StringBuilder stringBuilder = new StringBuilder();
        Random r = new Random();
        for(int i=0;i