Search in JTextarea

Question

Hello,
If I have a JTextarea and I display a whole book in it, is it possible to implement a search function. Like for example a JTextfield, where I could type a word and the press a button and all the matches in the JTextarea are highlited and the JTextarea goes to the first match.
Also, would it be possible to have a JComboBox with the chapters of the book, and then when I choose one, the JTextArea goes down to that chapter ?
If anybody can tell me if this is possible, and maybe give a few pointers or links, where I can read about this, I would be very thankful.

Answer 1

mollet wrote:
Hello,
If I have a JTextarea and I display a whole book in it, is it possible to implement a search function. Like for example a JTextfield, where I could type a word and the press a button and all the matches in the JTextarea are highlited and the JTextarea goes to the first match.Yes, this is certainly doable. For the highlighting of all matches, check out the javax.swing.text.Highlighter class. Use it to simply add a highlight around each matched word.
As far as actually finding all matches, a poor man's way of doing this would be to read the Document into a String, and do repeated String#indexOf(toFind) calls until -1 is returned. This method works, but is horribly inefficient for large documents, and runs the risk of OutOfMemoryErrors. You can use this method as a starting point and replace it with an improved algorithm later, if you want to keep working.
There are many ways of improving the efficiency of your search algorithm. For example, if you don't allow embedded newlines in your search text, you can scan for it by reading/scanning 1 line from the document at a time, as opposed to the entire document, thus quite probably eliminating your chance for OOME's. If you allow embedded newlines, or regex searches, things get more complicated.
Also, would it be possible to have a JComboBox with the chapters of the book, and then when I choose one, the JTextArea goes down to that chapter ?Certainly. Check out the Javadoc for the Document#createPosition() method. Use it to create one javax.swing.text.Position at the beginning of each chapter. Then, whenever they select an item from the JComboBox, simply move the caret to the position for the proper chapter. In fact, you really don't need to use Positions, you can just store the positions of the chapter starts in an array of ints if you want, for example. javax.swing.text.Positions area really useful if the document may change (text inserted or removed), but you want a relative location to be remembered.