重点是正则
String input = "abcdefghijk";
String input =
"abcdefghijk"
;
String regex =
"(.{2})"
input = input.replaceAll (regex,
"$1 "
);
System.out.println (input);
每两个字符串中插入字符串
原文：https://www.cnblogs.com/CHWLearningNotes/p/10315866.html
