Java buffered Read

I am working on a program for myself that shows all of the different ways to read in a text file. I have used FileWriter and BufferedWriter.

My question here is why does the FileWriter variable need to be wrapped in a BufferedWriter. I see this a lot in code and in some cases such as int wrapped in Integer. This makes sense to me here, but what does wrapping the FileWriter in a BufferedWriter gain.

    **FileWriter fWriter = new FileWriter(fileName);
    BufferedWriter bW = new BufferedWriter(fWriter);**

I found the code below on this site and I read through the comments and answers and found it to be somewhat help full

I think that the part is confusing is that there are a lot of different buffered reads for files. Which is the best way to read a file and why do they have to be wrapped in other objects. Does it can method support? Does it flush the buffers? Does it increase speed? (probably not) Is there some great advantage from wrapping files in a buffer.

    FileWriter fWriter = new FileWriter(fileName);
    BufferedWriter bW  = new BufferedWriter(fWriter);

In the above code the fWriter is created with the filename. then the fWriter variable is "wrapped" into the BufferedWriter bW variable. What really is the purpose of wrapping the FileWriter into the BufferedWriter.

  ---------------------------------------------------------
  -        FileWriter fw = new FileWriter (file);         -
  -        BufferedWriter bw = new BufferedWriter (fw);   - 
  -        PrintWriter outFile = new PrintWriter (bw);    - 
  ---------------------------------------------------------

Below is my complete file program. I only really had a question on the buffered wrappers but I thought that I would post it anyway that way if someone wants to compile it and run then they shouldn't have any trouble really.

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Locale;
import java.util.Scanner;

public class DDHExampleTextFileReader {
    List<String> lines = new ArrayList<String>();
    final static String FILE_NAME = "G:testFile.txt";
    final static String OUTPUT_FILE_NAME = "G:output.txt";
    final static Charset ENCODING = StandardCharsets.UTF_8;
    private static final int DEFAULT_BUFFER_SIZE = 1024 * 4;

    public DDHExampleTextFileReader() {
       //Zero argument constructor
    }

    private void fileReadOne() {
        String fileName = "G:testFile.txt"; // The name of the file to open.
        String line = null; // This will reference one line at a time

        try {
            // FileReader reads text files in the default encoding.
            // FileReader is meant for reading streams of characters. 
            // For reading streams of raw bytes, consider using a FileInputStream.
            FileReader fileReader = new FileReader(fileName);
            // Always wrap FileReader in BufferedReader.
            BufferedReader bufferedReader = new BufferedReader(fileReader);

                while((line = bufferedReader.readLine()) != null) {
                    System.out.println(line);
                }   

            bufferedReader.close();             // Always close files.
        }
        catch(FileNotFoundException ex) {
            System.out.println(
                "Unable to open file '" + 
                fileName + "'");                
        }
        catch(IOException ex) {
            System.out.println("Error reading file '" + fileName + "'");    
            ex.printStackTrace();
            // Or we could just do this: 
            // ex.printStackTrace();
        }
    }

    private void fileReadTwo() {
         // The name of the file to open.
        String fileName = "G:testFile.txt";

        try {
            // Use this for reading the data.
            byte[] buffer = new byte[1000];

            FileInputStream inputStream = 
                new FileInputStream(fileName);

            // read fills buffer with data and returns
            // the number of bytes read (which of course
            // may be less than the buffer size, but
            // it will never be more).
            int total = 0;
            int nRead = 0;
            while((nRead = inputStream.read(buffer)) != -1) {
                // Convert to String so we can display it.
                // Of course you wouldn't want to do this with
                // a 'real' binary file.
                System.out.println(new String(buffer));
                total += nRead;
            }   

            // Always close files.
            inputStream.close();        

            System.out.println("Read " + total + " bytes");
        }
        catch(FileNotFoundException ex) {
            System.out.println(
                "Unable to open file '" + 
                fileName + "'");                
        }
        catch(IOException ex) {
            System.out.println(
                "Error reading file '" 
                + fileName + "'");                  
            // Or we could just do this: 
            // ex.printStackTrace();
        }
    }

    private void fileReadThree() {
        String content = null;
           File file = new File("G:testFile.txt"); //for ex foo.txt
           FileReader reader = null;
           try {
               reader = new FileReader(file);
               char[] chars = new char[(int) file.length()];
               reader.read(chars);
               content = new String(chars);
               System.out.println(content);
           } catch (IOException e) {
               e.printStackTrace();
           } finally {
               try {
                reader.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
           }
    }

    private void fileReadFour() {
       File f = new File("G:testFile.txt");
            String text = "";
            int read, N = 1024 * 1024;
            char[] buffer = new char[N];

            try {
                FileReader fr = new FileReader(f);
                BufferedReader br = new BufferedReader(fr);

                while(true) {
                    read = br.read(buffer, 0, N);
                    text += new String(buffer, 0, read);

                    if(read < N) {
                        break;
                    }
                }
            } catch(Exception ex) {
                ex.printStackTrace();
            }
           System.out.println(text);
        }

    //Doesn't keep file formatting
    private void fileReadfive() {
          Scanner s = null;
            try {
                try {
                    s = new Scanner(new BufferedReader(new FileReader("G:testFile.txt")));
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                }
                    while (s.hasNext()) {
                        System.out.println(s.next());
                    }
            } finally {
                if (s != null) {
                    s.close();
                }
            }
    }

    private void fileReadSumsTheFileOfNumbersScanner() {
        Scanner s = null;
        double sum = 0;

        try {
            try {
                s = new Scanner(new BufferedReader(new FileReader("G:n.txt")));
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }
            s.useLocale(Locale.US);

            while (s.hasNext()) {
                if (s.hasNextDouble()) {
                    sum += s.nextDouble();
                } else {
                    s.next();
                }   
            }
        } finally {
            s.close();
        }
        System.out.println(sum);
    }

    private void fileWriterOneTextFile() {
        String fileName = "G:testTemp.txt";
        try {
            // Assume default encoding.
            /*
             Whether or not a file is available or may be created depends upon the underlying platform. Some platforms, in particular, 
             allow a file to be opened for writing by only one FileWriter (or other file-writing object) at a time. In such 
             situations the constructors in this class will fail if the file involved is already open. 
             FileWriter is meant for writing streams of characters. For writing streams of raw bytes, consider using a 
             FileOutputStream.
             */
            FileWriter fWriter = new FileWriter(fileName);
            // Always wrap FileWriter in BufferedWriter.
            /*
             The buffer size may be specified, or the default size may be accepted. The default is large enough for most purposes.
             A newLine() method is provided, which uses the platform's own notion of line separator as defined by the system 
             property line.separator. Not all platforms use the newline character ('\n') to terminate lines. Calling this method 
             to terminate each output line is therefore preferred to writing a newline character directly. 
             In general, a Writer sends its output immediately to the underlying character or byte stream. Unless prompt output 
             is required, it is advisable to wrap a BufferedWriter around any Writer whose write() operations may be costly, such as 
             FileWriters and OutputStreamWriters. For example, 
                PrintWriter out
                    = new PrintWriter(new BufferedWriter(new FileWriter("foo.out")));
             will buffer the PrintWriter's output to the file. Without buffering, each invocation of a print() method would cause 
             characters to be converted into bytes that would then be written immediately to the file, which can be very inefficient.
             */
            BufferedWriter bW = new BufferedWriter(fWriter);
            // Note that write() does not automatically
            // append a newline character.
            bW.write("This is a test string that will be written to the file!!!!");
            bW.write("This more text that will be written to the file!!!!");
            bW.newLine();
            bW.write("After the newLine bufferedWriter method.");
            bW.write(" A   B   C D E         F     G");
            bW.newLine();
            bW.write("Hauf");
            bW.close();
        } catch(IOException ex) {
            System.out.println("Error writing to file '" + fileName + "'");
            ex.printStackTrace();
        }
    }

     List<String> readSmallTextFile(String aFileName) throws IOException {
            Path path = Paths.get(aFileName);
            return Files.readAllLines(path, ENCODING);
          }

          void writeSmallTextFile(List<String> aLines, String aFileName) throws IOException {
            Path path = Paths.get(aFileName);
            Files.write(path, aLines, ENCODING);
          }

          //For larger files
          void readLargerTextFile(String aFileName) throws IOException {
            Path path = Paths.get(aFileName);
            try (Scanner scanner =  new Scanner(path, ENCODING.name())){
              while (scanner.hasNextLine()){
                //process each line in some way
                log(scanner.nextLine());
              }      
            }
          }

          void readLargerTextFileAlternate(String aFileName) throws IOException {
            Path path = Paths.get(aFileName);
            try (BufferedReader reader = Files.newBufferedReader(path, ENCODING)){
              String line = null;
              while ((line = reader.readLine()) != null) {
                //process each line in some way
                log(line);
              }      
            }
          }

          void writeLargerTextFile(String aFileName, List<String> aLines) throws IOException {
            Path path = Paths.get(aFileName);
            try (BufferedWriter writer = Files.newBufferedWriter(path, ENCODING)){
              for(String line : aLines){
                writer.write(line);
                writer.newLine();
              }
            }
          }

          private static void log(Object aMsg){
            System.out.println(String.valueOf(aMsg));
          }

    public static void main(String[] args) throws IOException {
        DDHExampleTextFileReader doug = new DDHExampleTextFileReader();
        List<String> lines = doug.readSmallTextFile(FILE_NAME);
        //doug.fileReadOne();
        //doug.fileReadTwo();
        //doug.fileReadThree();
        //doug.fileReadFour();
        //doug.fileReadfive();
        //doug.fileReadSumsTheFileOfNumbersScanner();
        doug.fileWriterOneTextFile();
        log(lines);
            lines.add("This is a line added in code.");
            doug.writeSmallTextFile(lines, FILE_NAME);

            doug.readLargerTextFile(FILE_NAME);
            lines = Arrays.asList("Down to the Waterline", "Water of Love");
            doug.writeLargerTextFile(OUTPUT_FILE_NAME, lines);



        System.out.println(String.valueOf("\n\n\n-----End of Main Method!!!------"));
    }
}


/*
public static void copy(Reader input, OutputStream output, String encoding)
                   throws IOException {
               if (encoding == null) {
                    copy(input, output);
                } else {
                    OutputStreamWriter out = new OutputStreamWriter(output, encoding);
                    copy(input, out);
                    // XXX Unless anyone is planning on rewriting OutputStreamWriter,
                    // we have to flush here.
                    out.flush();
                }
     }

    public static void copy(Reader input, OutputStream output)
                    throws IOException {
                OutputStreamWriter out = new OutputStreamWriter(output);
                copy(input, out);
                // XXX Unless anyone is planning on rewriting OutputStreamWriter, we
                // have to flush here.
                out.flush();
     }

     public static int copy(Reader input, Writer output) throws IOException {
                  //  long count = copyLarge(input, output);
                    //copy large
                    byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
                    long count = 0;
                    int n = 0;
                    while (-1 != (n = input.read())) {
                        output.write(0);
                        count += n;
                    }

                    //end copy large
                    if (count > Integer.MAX_VALUE) {
                        return -1;
                    }
                    return (int) count;
    }

    public static long copyLarge(InputStream i, OutputStream o) throws IOException {
            byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
            long count = 0;
            int n = 0;
            while (-1 != (n = i.read(buffer))) {
              o.write(buffer, 0, n);
              count += n;
            }
        return count;
    }

    public static String toString(InputStream input) throws IOException {
                    StringWriter sw = new StringWriter();
                     copy(input, sw);
                     return sw.toString();
    }

    public static void copy(InputStream input, Writer output) throws IOException {
              InputStreamReader in = new InputStreamReader(input);
          copy(in, output);
    }


    public static void copy(InputStream input, Writer output, String encoding) throws IOException {
                if (encoding == null) {
                    copy(input, output);
                } else {
                    InputStreamReader in = new InputStreamReader(input, encoding);
                    copy(in, output);
                }
     }