Dangling meta character '?' near index 0

Problem

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);