Java byte array and string conversion issues

Today, when you use the byte stream to copy a picture, there is a problem, that is, when you convert an array of bytes to a string, there is a different length. This is actually a wrong operation.

 public static void Main (string[] args) throws IOException {//First way (no problem)/*fileinputstream FIS = new fileinputs    Tream ("d:\\ belle. jpg");    FileOutputStream fos = new FileOutputStream ("f:\\ccc\\ belle. jpg");    int Len;    while (len = Fis.read ())! =-1) {fos.write (len);    } fos.close ();    Fis.close (); *///The second way, there will be a problem/*fileinputstream FIS = new FileInputStream ("d:\\ belle. jpg");    byte[] arr = new byte[1024 * 6];    int Len;    StringBuilder sb = new StringBuilder ();    while (len = Fis.read (arr))! =-1) {Sb.append (new String (Arr,0,len));    } fileoutputstream fos = new FileOutputStream ("f:\\ccc\\ belle. jpg");    Fos.write (Sb.tostring (). GetBytes ());    Fos.close ();            Fis.close (); *///Third way to solve the problem fileinputstream FIS = new FileInputStream ("d:\\ belle. jpg");    byte[] arr = new byte[1024 * 6];    int Len;    StringBuilder sb = new StringBuilder ();    while (len = Fis.read (arr))! =-1) {Sb.append (new String (Arr,0,len, "iso-8859-1"));  }  FileOutputStream fos = new FileOutputStream ("f:\\ccc\\ belle. jpg");    Fos.write (Sb.tostring (). GetBytes ("iso-8859-1"));    Fos.close (); Fis.close ();}

The reason for this is that when you use a character array to read a picture and convert it to a string type, it is converted using the editor's default encoding, but the default encoding method (UTF-8 or other)
Garbled (the reason is that multiple bytes into characters when the Code table does not know, will appear?), so the length will increase a lot. And when using iso-8859-1, it is a byte-by-byte conversion, the following write
Time to specify the encoding, which is equivalent to a reversal, so no problem occurred

Java byte array and string conversion issues