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Thread: String[] to String

  1. #1
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    Default 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".


  2. #2
    Administrator copeg's Avatar
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    Default Re: String[] to String

    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();

  3. #3
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    Default Re: String[] to String

    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);

  4. #4
    Administrator copeg's Avatar
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    Default Re: String[] to String

    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)

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    Junior Member srikrish85's Avatar
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    Default Re: String[] to String

    Use StringBuilder to do the task

  6. #6
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    Default Re: String[] to String

    Quote Originally Posted by copeg View Post
    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).

  7. #7
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    Default Re: String[] to String

    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.

  8. The Following User Says Thank You to aisthesis For This Useful Post:

    The_Mexican (February 19th, 2011)

  9. #8
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    Default Re: String[] to String

    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

  10. #9
    Administrator copeg's Avatar
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    Default Re: String[] to String

    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");
    }

  11. The Following User Says Thank You to copeg For This Useful Post:

    The_Mexican (February 19th, 2011)

  12. #10
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    Default Re: String[] to String

    Thanks, it works now.

  13. #11
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    Default Re: String[] to String

    You can also use Apache Lang library:
    org.apache.commons.lang.StringUtils:
    method join.
    So:
    StringUtils.join(array, "");
    does the job.

  14. The Following User Says Thank You to codesmuggler For This Useful Post:

    javapenguin (February 19th, 2011)

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