Is it possible to open a txt file?

[jason27131]

I am currently trying to make a database, and im storing all the info in a txt file. I want to user to be able to open the txt file and edit any line they want. Just wondering, but is it possible to open a txt file with java? if not, can you give me some ideas.

[Josiah.Haswell]

It's very possible. Try looking at the FileReader and FileWriter APIs.

Here's a quick example:

Code:

		BufferedReader br;
		try
		{
			br = new BufferedReader(new FileReader("test.txt"));
			int ch;
			while((ch = br.read()) != -1)
                               dostuff(ch);
		}
		catch (FileNotFoundException ex)
		{
			ex.printStackTrace();
		}
		catch(IOException ex)
		{
			ex.printStackTrace();
		}

[Josiah.Haswell]

Eh. Are there code-formatting tags available?

[jason27131]

no what i meant is opening as in double clicking the txt file. i don't mean editing it in java.

[Josiah.Haswell]

Ah. Ok.

Well, you'll have to provide some means of accessing the file. For example, you can use a JFileChooser to allow the user to browse to the file, and upon opening it, you can use a FileReader to read it into a Document or a String, and then add that Document or String to a text widget (JTextArea, JEditorPane, etc.).


Here are some resources that I hope will help you:

JFileChooser tutorial:
How to Use File Choosers (The Java™ Tutorials > Creating a GUI with JFC/Swing > Using Swing Components)

Text Component tutorials:

Using Text Components (The Java™ Tutorials > Creating a GUI with JFC/Swing > Using Swing Components)

Good luck!

Joe

[jason27131]

thanks. your a life saver

[levent]

Quote:

Eh. Are there code-formatting tags available?

Yes. Check your previous message. I placed it inside [code] tag.

[Josiah.Haswell]

You're welcome!

Joe

[jason27131]

actually, never mind. its kinda too hard. to incoporate 3 classes together, and i don't know how. Can you tell me how to edit a specific line or word to another in a txt file?

[Josiah.Haswell]

Um. You can edit the file stream directly. Here's an example that will replace every instance of one word with an instance of another:

Code:

		BufferedReader br = new BufferedReader(new FileReader("<path to source file>"));
		BufferedWriter bw = new BufferedWriter(new FileWriter("<path to destination file>"));
		String str;
		
		while((str = br.readLine()) != null)
		{
			str.replaceAll("oldword", "newword");
			bw.write(str);
		}
		br.close();
		bw.flush();
		bw.close();

I sincerely hope I'm not doing your homework for you. Sorry, but my time on the Sun Java Forums has made me skeptical :/

Joe

P.S. Thanks for the code hint

[jason27131]

na, my homework has only about 100 more lines of coding to do. im trying to make a database, and the code you just told me is suppose to help me edit the last name and address of a person incase they are married.

[Josiah.Haswell]

Ok. Good luck. I don't know that such an indiscriminate find-and-replace method will work very well, but I hope it's useful/gives you an idea about file IO.

Joe

[jason27131]

ok umm, i have no idea how to use the code u gave me.

[jason27131]

it doesn't compile with a class.

[Josiah.Haswell]

Ok. Firstly, the code needs to throw or catch several exceptions, specifically a FileNotFoundException and an IOException (Although the IOException will catch the FileNotFoundException, catching the FileNotFoundException will give you a better idea of what's going wrong).

So, create a class, e.g.

Code:

public class StringReplace
{

public StringReplace()  //Constructor
{
}

public void replaceString() throws FileNotFoundException, IOException
{
		BufferedReader br = new BufferedReader(new FileReader("<path to source file>"));
		BufferedWriter bw = new BufferedWriter(new FileWriter("<path to destination file>"));
		String str;
		
		while((str = br.readLine()) != null)
		{
			str.replaceAll("oldword", "newword");
			bw.write(str);
		}
		br.close();
		bw.flush();
		bw.close();
}
}

[jason27131]

when u say path to source file, and path to destination file, what do u mean?

[Josiah.Haswell]

Find the location of the file on the disk, ex. "C:\Documents and Settings\testfile.txt" and, in its place in the program, enter "C:\\Documents and Settings\\testfile.txt".

Joe

[jason27131]

just wondering, but why won't this compile.

CODE:

import java.io.*;

public class DB{
String s = "DataBase.txt";
public static void display(String s) throws IOException{
FileReader fr = new FileReader(s);
BufferedReader br = new BufferedReader(fr);
String line = br.readline();
while (line ! = null){
line = br.readline();
}
br.close();
fr.close();
}

public void find(){
String phrase = line;
String word = JOptionPane.showInputDialog (null, "Please enter the word you are looking for", "Find", JOptionPane.OK_CANCEL_OPTION);
}
}


ERROR:

[line: 9]
Error: ')' expected

[Josiah.Haswell]

It won't compile because you have a space between the ! and the = in the operatior !=.

[jason27131]

k i did that, but more errors come up.

CODE

import java.io.*;

public class DB{
public static void display(String s) throws IOException{
FileReader fr = new FileReader(s);
BufferedReader br = new BufferedReader(fr);
String line = br.readline();
while (line != null){
line = br.readline();
}
br.close();
fr.close();
}
}

ERROR

File: C:\Documents and Settings\David\Desktop\jason's homework. DO NOT DELETE\Java Programming\DB.java [line: 7]
Error: cannot find symbol
symbol : method readline()
location: class java.io.BufferedReader
File: C:\Documents and Settings\David\Desktop\jason's homework. DO NOT DELETE\Java Programming\DB.java [line: 9]
Error: cannot find symbol
symbol : method readline()
location: class java.io.BufferedReader