//隐藏手机号码中间四位
String phoneNumber = "15567893456";
String resultPhone= phoneNumber.replaceAll("(\\d{3})\\d{4}(\\d{4})","$1****$2");
System.out.println("隐藏后的手机号：" + resultPhone);
//隐藏邮箱
String email = "654212@qq.com";
String resultEmail = email.replaceAll("(\\w?)(\\w+)(\\w)(@\\w+\\.[a-z]+(\\.[a-z]+)?)", "$1****$3$4");
System.out.println("隐藏后的邮箱：" + resultEmail);
//隐藏身份证
String idCard = "420116199302220456";
String resultIdCard = idCard.replaceAll("(\\d{4})\\d{10}(\\w{4})","$1*****$2");
System.out.println("隐藏后的身份证号：" + resultIdCard);

# insert(a,n1,n2,str)的参数解析如下
@ a：字段名.
@ n1：开始替换的位置.
@ n2：替换的长度.
@ str：替换后的字符串.

select insert(phone,4,4,‘****‘) as phone from user