Regular Expression Tester - User Guide

Features

• Test and search for regular expression
• Matches are colorized, for an easy visual clue
• Support for pattern flags (e.g. Pattern.DOTALL)
• LiveEval evaluates your regular expression while you are typing it, gives feedback on possible errors and shows any matches automatically
• LiveEval is supported for changes of the regular expression, the search text and the pattern flags
• Generation of string literals based on the regexp, e.g. "/(x/)" becomes "//(x//)"
• Code Generation based on the regex and pattern flags, e.g. "/(x/)" and DOTALL becomes "Pattern.compile("//(x//)",Pattern.DOTALL);"
• Easy movement through matches: Choose "Previous Match" or "Next Match" and cycle through all matches found. Right click on a match, select "Goto Match" and the result text box will show you the results for this particular match.
• Polished and accessible user interface, everything is reachable via keyboard

Testing a Regular Expression

• Enter a regex in the upper text field, labeled "Regular Expression"
• Enter a search text in the second, bigger text field. This text will be used to evaluate the regular expression.
• Press the "Find RegEx" button
• If there were any matches, they will be marked with a red color within the search text. The result area will show you the total number of matches. It also lists the match's start and end positions within and the actual text found
• If there were no matches, you will get the message "No matches found!" inside the result area
• To clear all text fields, you can press the "Clear" button in the view's toolbar

Moving Through Matches

If you got a lot of matches, you may want to navigate through them. This can be done by using the arrows in the views tool bar. Choose "Next Match" to move the selection to the next match. Choose "Previous Match" to go back to the previous match found. The result area will also show the match's relevant entries.

Another way to navigate to a certain match is to put the cursor inside a marked match or draw a selection on it. Then right click to see the context menu and choose Go To Match. Now the result area will show you the result data belonging to this particular match.

LiveEval

LiveEval is a comfortable way to continiously test your regex. If it is activated, everytime you change something in your regex the program re-evaluates it and shows its results. This also works if you do not touch the regex, but change the search text or choose any of the pattern flags. You always get a live feedback if your changes led to the right result or not.

Pattern Flags

Menu Item	Java Pattern Flag	Description
Canonical Equivalence	Pattern.CANON_EQ	When this flag is specified then two characters will be considered to match if, and only if, their full canonical decompositions match.
Case Insensitive	Pattern.CASE_INSENSITIVE	Enables case-insensitive matching.
Comments	Pattern.COMMENTS	Permits whitespace and comments in pattern.
Dotall Mode	Pattern.DOTALL	In dotall mode, the expression . matches any character, including a line terminator.
Multiline Mode	Pattern.MULTILINE	In multiline mode the expressions ^ and $ match just after or just before, respectively, a line terminator or the end of the input sequence.
Unicode Case	Pattern.UNICODE_CASE	Enables Unicode-aware case folding.
Unix Lines	Pattern.UNIX_LINES	In this mode, only the '\n' line terminator is recognized in the behavior of ., ^, and $.

Code Generation

If you want to use your regular expression as a literal String in your Java code, you might find yourself in trouble. Your trouble maker #1 here is the backslash ("\"). In Strings backslashes are used to escape certain kind of characters, e.g \n for a new line or \t for a tab. Java only allows certain characters to be followed by a backslash. So if you use any backslahes in your regular expression you will either get a compile error because Java does not accept the following character or your regex will be mis-interpreted. What you have to do is to escape every backslash with another backslash so Java can safely ignore them, e.g. /(x/) becomes //(x//).

To help you with this task, right click on your regular expression and choose Copy As String Literal. Now you can paste the escaped regex anywhere in your code.

If you would like additional help with code generation, you can also choose Copy As Java Declaration from the regex's context menu. This will escape the regex as described above and create the neccessary Java code. For example if your regex is /(x/) and you chose the pattern flag Dotall Mode you will get Pattern.compile("//(x//)",Pattern.DOTALL); which you can paste anywhere you like.

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