Thread: String[] to String

Hi, I would like to convert a String array (String[]) to a String which I can print. I don't know how to do this as there's no simple method like String s = stringArray.toString() or something as far as I know. What I'm trying to do is read a text file which has multiple lines and store the entire text file as one variable which I can then include in a JOptionPane statement.

Here is some relevant code:

FileInputStream fis = null;
            BufferedInputStream bis = null;
            DataInputStream dis = null;
            FileInputStream fis2 = null;
            BufferedInputStream bis2 = null;
            DataInputStream dis2 = null;
			try {
				//Reading file
				fis = new FileInputStream(rfile);
                bis = new BufferedInputStream(fis);
                dis = new DataInputStream(bis);
                fis2 = new FileInputStream(rfile);
                bis2 = new BufferedInputStream(fis);
                dis2 = new DataInputStream(bis);
                String aLine;
                int num = 0;
                while(dis.readLine() != null)
                {
                	num++;
                }
                String[] notesarr = new String[num];
                for(int i=0; i < num; i++)
                {
                	notesarr[i] = dis2.readLine();
                }
                //Display notes
    			JOptionPane.showMessageDialog(null, "Notes: \n"+notesarr,"Notes",JOptionPane.INFORMATION_MESSAGE);
    			System.exit(0);
			} catch (IOException e) {}

This doesn't work though because when I print notesarr in the JOptionPane statement it just comes out as "[Ljava.lang.String;@affc70".

Use a StringBuilder or StringBuffer, appending the lines as you loop through the array (or read the file). Then just convert to a string

StringBuffer sb = new StringBuffer();
String[] lines = {"test1", "test2"};
for ( int i = 0; i < lines.length; i++ ){
     sb.append(lines[i]);
}
String mystring = sb.toString();

For some reason, when I do this, it prints out: "nullnull". I have no idea why.

StringBuffer sb = new StringBuffer();
                String[] notesarr = new String[num];
                for(int i=0; i < num; i++)
                {
                	notesarr[i] = dis2.readLine();
                	sb.append(notesarr[i]);
                }
                notes = sb.toString();
                //Display notes
    			JOptionPane.showMessageDialog(null, "Notes: \n"+notes,"Notes",JOptionPane.INFORMATION_MESSAGE);
    			System.exit(0);

You may have to post more code...where does the variable num come from? If you've read the file already then readLine returns null (and this nulls are appended to the StringBuffer)

Use StringBuilder to do the task

Originally Posted by copeg

You may have to post more code...where does the variable num come from? If you've read the file already then readLine returns null (and this nulls are appended to the StringBuffer)

Hmm, technically I did read the file once, to get the value of num (which is just the number of lines in the file). However, I used two different readers to do this (see the code in my first post).

Wouldn't it clean things up quite a bit to do this:

BufferedReader in = new BufferedReader(new FileReader(rfile));
StringBuilder text = new StringBuilder();
try {
   while (in.ready()) {
      text.append(in.readLine());
   }
   JOptionPane(...);
} catch (IOException e) {
   System.err.println(e.getMessage());
}  finally {
   in.close();
}

I see no need even to create an array of strings, and I don't really like this build-up of objects for reading files. BufferedReader() does everything you need imo.

That makes it work. However, when I print the text, it strings all the lines in the text together, with no enters to separate lines.

This is the text file:

One
Two
Three
Four
Five

When I run this line:

JOptionPane.showMessageDialog(null, "Notes: \n"+text,"Notes",JOptionPane.INFORMATION_MESSAGE);

The output is:

Notes:
OneTwoThreeFourFive

technically I did read the file once, to get the value of num (which is just the number of lines in the file). However, I used two different readers to do this (see the code in my first post).

There shouldn't be a need to read the file twice.

That makes it work. However, when I print the text, it strings all the lines in the text together, with no enters to separate lines.

Append a new line

while ( //reading ){
    text.append(in.readLine());
    text.append("\n");
}

Thanks, it works now.