替换两数字间的英文字母：
e.g. “2a3”—->”23”
反向引用
rs = rs.replaceAll(“(\\d)([a-zA-Z])(\\d)”,“$1$3”);
环视
rs = rs.replaceAll(“(?<=\\d)[a-zA-Z](?=\\d)”,“”);
rs = rs.replaceAll(“(\\d)([a-zA-Z])(\\d)”,“$1$3”);
rs = rs.replaceAll(“(?<=\\d)[a-zA-Z](?=\\d)”,“”);
