Regex to find email address

**TechGate** · 05-02-2010

Hello,
I use a regular expression to find all email addresses that are found in a text file. Here is my source code

Code:

String txt;
ArrayList ls = <String> new ArrayList <String>(0);
FileReader in;
try
	{
	in = new FileReader("/ locations / file.txt");
	}
catch (FileNotFoundException e)
	{
	throw new Exception("Unable to open file"E);
	}
/ / Iterate over the file
int c;
try
	{
	while ((c = in.read()) != -1)
		{
		txt = txt + (char) c;
		}
	}
catch (IOException e)
	{
	throw new Exception("Unable to read file"E);
	}
 
/ / Definition of regexp
AChercher Pattern = Pattern.compiles("[_A-Za-z0-9-] + (\\. [_A-Za-z0-9-]+)*@" +
		"[A-Za-z0-9-] + (\\. [A-Za-z0-9-]+)*(\\. [_A-Za-z0-9-] +) ");
mth = aChercher researcher.matcher(txt);
		
/ / Search the address
while (researcher.find())
	{
	String email = researcher.group();
ls.add(email);
	}

But this is not working for me, I request that you just go through the code and see if you have missed something. And please guide me if I have mistaken somewhere.

**Windowed** · 05-02-2010

Hello,
Can you show the code to display your list?
- It is better to define your list as a List:

Code:

      List list = <String> new ArrayList <String>();

- Why put all your file in a buffer character by character? You could read line by line and do your search loop line.
Display the code and then we can help you.

**TechGate** · 05-02-2010

Hello,
To test, I write System.out.println facility directly via:

Code:

for (<String> Iterator it = list.ietrator(); It.hasNext();)
	{
	System.out.System.out.println(it.next());			
	}

But if I display in a JTable and the result is the same. Character by character or line back to the same right? I suppose the method that returns line by line reads the character 1 by 1 to find a line so it should not be any difference in speed and resource use.

**Linux-Us** · 05-02-2010

Hello,
Instead of declaring the string like this:

Code:

String text;
/ / I:
String text = "";

I think it is better to declare the string in this way

Code:

text = text + (char) c;
/ / Has returned to
text = null + (char) c;
/ / 1st character

I hope this is going to help you. If you have any more queries then post with them.

**GlassFish** · 05-02-2010

Hello,
If you want to fill a string that contains the entire contents of the file

Code:

text = text + (char) c;

This creates a new string to each character! Use a StringBuilder and append ()!
Why not read character by character:
- If you want to read one character at a time, why not! But you want to read lines.
- Then you go to store all your files when you have no need, even if you have lots of memory.
- With a good old BufferedReader, a loop readline () and search the current line is cleaner.
- Your file is small, your code works, but it is always better to be ready for the large files.

**TechGate** · 05-02-2010

Hello,
Thanks for the replies but actually I'll use StringBuilder. This is not a bad idea to research the addresses in the line and then move to the next line. But I will have a design issue, reading this in a class and research in another. I use the pattern 'template method'. But I can look to change the design to allow it. If you have any other alternative solution for doing the same then please do post back.