Buttercola: LinkedIn: Text file Iterable

Buttercola: LinkedIn: Text file Iterable
Question:Implement a (Java) Iterable object that iterates lines one by one from a text file..

public class TextFile implements Iterable<String>

{

  public TextFile(String fileName) { // please implement this

  /** Begin reading the file, line by line.

    * The returned Iterator.next() will return a line.

    */

  @Override

  public Iterator<String> iterator() { // please implement this

public class TextFile implements Iterable<String> {

    Scanner scanner;

    public TextFile(String fileName) {

        try {

            scanner = new Scanner(new File(fileName));

        } catch (Exception e) {

             

        }

    }

  /** Begin reading the file, line by line.

   *  The returned Iterator.next() will return a line.

   */

    @Override

    public Iterator<String> iterator() {

        return new TextFileIterator();

    }

     

    private class TextFileIterator implements Iterator<String> {

        @Override

        public boolean hasNext() {

            return scanner.hasNext();

        }

         

        @Override

        public String next() {

            return scanner.nextLine();

        }

         

        @Override

        public void remove() {

            throw new UnsupportedOperationException();

        }

    }

}

http://blog.csdn.net/craiglin1992/article/details/44778643

ANSWER: An implementation of this using bufferedReader:

public class TextFile implements Iterable<String>{

        private BufferedReader br;

        public TextFile(String fileName) throws FileNotFoundException {
            br = new BufferedReader(new FileReader(fileName));
        }

        @Override
        public Iterator<String> iterator() {
                return new Iterator<String>() {
            @Override
            public boolean hasNext() {
                try {
                    br.mark(1);
                    if (br.read() < 0) {
                        return false;
                    }
                    br.reset();
                    return true;
                } catch (IOException e) {
                    return false;
                }
            }

            @Override
            public String next() {
                try {
                    return br.readLine();
                } catch (IOException e) {
                    return null;
                }
            }
            @Override
            public void remove() {
                throw new UnsupportedOperationException();
            }

        };
        }
}

http://stackoverflow.com/questions/8240071/what-is-mark-and-reset-in-bufferedreader

The mark() marking a particular point in a stream and reset() resets the stream to the most recent mark. These methods provide a book-marking feature that allows you to read ahead in the stream to inspect the upcoming data.

From this documentation:

The mark() method mark a position in the input to which the stream can be "reset" by calling the reset() method. The parameter readLimit is the number of chars that can be read from the stream after setting the mark before the mark becomes invalid. For example, if mark() is called with a read limit of 10, then when 11 chars of data are read from the stream before the reset() method is called, then the mark is invalid and the stream object instance is not required to remember the mark. Note that the number of chars that can be remembered by this method can be greater than the size of the internal read buffer. It is also not dependent on the subordinate stream supporting mark/reset functionality.

Streams can't naturally be "unread" to go backwards. Mark/reset provides a way to emulate that if needed.

Once you call mark() it will begin remembering data you read from that point forwards in memory. When you call reset() it will jump back to the marked position, by satisfying future read()s from the in the in-memory buffer. If you read past the end of that buffer, then it will seamlessly go back to reading fresh data from the underlying "in" reader that the BufferedReader was created with.

http://www.cnblogs.com/jxlgetter/p/4395098.html
http://plse.cs.washington.edu/daikon/staging-daikon/download/api/src-html/daikon/util/TextFile.html
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