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);