Java Language
- Getting started with Java Language
- Top 10 Java Errors with Solutions
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Java Language Regular Expressions Escape Characters
Example
Generally
To use regular expression specific characters (?+| etc.) in their literal meaning they need to be escaped. In common regular expression this is done by a backslash \. However, as it has a special meaning in Java Strings, you have to use a double backslash \\.
These two examples will not work:
"???".replaceAll ("?", "!"); //java.util.regex.PatternSyntaxException
"???".replaceAll ("\?", "!"); //Invalid escape sequence
This example works
"???".replaceAll ("\\?", "!"); //"!!!"
Splitting a Pipe Delimited String
This does not return the expected result:
"a|b".split ("|"); // [a, |, b]
This returns the expected result:
"a|b".split ("\\|"); // [a, b]
Escaping backslash \
This will give an error:
"\\".matches("\\"); // PatternSyntaxException
"\\".matches("\\\"); // Syntax Error
This works:
"\\".matches("\\\\"); // true
