android 读写文件

FileInputStream fin = new FileInputStream(fDown);
int length = fin.available();
byte [] buffer = new byte[length];
fin.read(buffer);
sUUID = new String(buffer, "UTF-8");
fin.close();

FileInputStream filestream = new FileInputStream(new File(fDown.getPath()));
byte[] buff= new byte[1024];
int hasRead = 0;
StringBuilder sb = new StringBuilder("");
while((hasRead = filestream.read(buff))>0)
{
sb.append(new String(buff,0,hasRead));
}
filestream.close();
sUUID = sb.toString();