Чтение текстового файла в строку используя NIO

//Чтение текстового файла в строку используя NIO
//Используется java.nio.channels.FileChannel, java.nio.MappedByteBuffer;
//java.nio.CharBuffer;,java.nio.charset.CharsetDecoder;
package readFile;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;

public class Read2 {
 private static Charset charset = Charset.forName("utf-8");
 private static CharsetDecoder decoder = charset.newDecoder();

 static String readFile(String filename , String str){
        FileInputStream fileInputStream;
        FileChannel fileChannel;
        StringBuffer sb = new StringBuffer(2048);
        StringBuilder sbl=new StringBuilder(2048);
        long fileSize;
        MappedByteBuffer mBuf;

    try {
      fileInputStream = new FileInputStream(filename); 
      fileChannel = fileInputStream.getChannel();
      fileSize = fileChannel.size();
      mBuf = fileChannel.map(FileChannel.MapMode.READ_ONLY, 0, fileSize);
       CharBuffer cb = decoder.decode(mBuf);
    while (cb.hasRemaining())
    {
        sbl.append(String.valueOf((char)cb.get()));
    }
      fileChannel.close();
      fileInputStream.close();
    } catch (IOException exc) {
      System.out.println(exc);
      System.exit(1);
    }
        return sbl.toString();
    }

public static void main(String[] args) {

    String fl="/MyDir/myfile.txt";
    String out="";
    long start = System.currentTimeMillis(); // start timing
    out=readFile("/MyDir/myfile.txt" , "");
    System.out.println("out  "+out);
    long stop = System.currentTimeMillis(); // stop timing
    System.out.println("TimeMillis: " + (stop - start)); 
   
  }


}