Thread: "?" replacement

I'm making the encryption program mentioned in my other post. When I type all other character besides " ' /\ and . it works fine besides the question mark. It gives me this error when ever i type in a question mark:

Options:
---------------
|1. Encryption|
|2. Decryption|
---------------

Enter your choice:
1

Enter the phrase you want encrypted:
?
Exception in thread "main" java.util.regex.PatternSyntaxException: Dangling meta
character '?' near index 0
?
^
at java.util.regex.Pattern.error(Unknown Source)
at java.util.regex.Pattern.sequence(Unknown Source)
at java.util.regex.Pattern.expr(Unknown Source)
at java.util.regex.Pattern.compile(Unknown Source)
at java.util.regex.Pattern.<init>(Unknown Source)
at java.util.regex.Pattern.compile(Unknown Source)
at java.lang.String.replaceAll(Unknown Source)
at encryption.main(encryption.java:376)
Press any key to continue . . .

This is the code for replacing the ?:

			if (pdphrase.contains("?")) {
 
				pdphrase = pdphrase.replaceAll("?", "24");
 
			}

I don't know whats going on or if I should just scrap that character like i did others. The period caused every number to change it its number and the other ones caused errors when compiling. Please Help!

String.replace uses Java's Regex engine which uses those characters (actually, I think there are a few other characters such as *) for special behaviors.

The simple solution is to manually search the string yourself, or to ensure that the user enters a valid Java Regex pattern. See: Lesson: Regular Expressions (The Java™ Tutorials > Essential Classes)