Dangling meta character '?' near index 0

Problem

转载自：http://www.javagalaxy.com/forum/viewtopic.php?p=377&sid=2d2152ff1ee06bc37c31b4b40e9a6fad

String str = "testing??";

str = str.replaceAll("?", "");

When you use the above pattern you get an exception as "Dangling meta character '?' near index 0"


Solution

String str = "testing??";

str = str.replaceAll("\\?", "");

You can use the above solution when you are replacing * and + symbols

String str = "testing??*+";

str = str.replaceAll("\\*", ""); //"Dangling meta character '*' near index 0"
str = str.replaceAll("\\+", ""); //"Dangling meta character '+' near index 0"

 

+、*、|、/等符号在正则表达示中有相应的不同意义。
一般来讲只需要加[]、或是//即可

int i=s.split("[?]").length;

或者

int i=s.split("\\?").length;i);