Would someone tell me the fuzzy concept

Question

I try to use java to read a file about 16Mb to a string, first it's out of memory, and then I increase the heap use -mx200000000, make it to about 200Mb. It can handle the file, but it still take about 20-30 seconds to read it. and I use another tool like textpad to open it, after i click the filename,it open thoroughly soon. To me it's hard to understand why it takes a short time to read it. and my program can not?
but I wonder the factors that affect the speed of reading a file is my program or java's limitation. If you have any idea or hypothesis, would you please tell me, make me know more about it?
my program like this:
fis = new FileInputStream (fileName);
int size = fis.available ();
byte[] bytes = new byte [size];
fis.read (bytes);
str = new String (bytes);

Answer 1

You need to use a BufferedInputStream and then read from the buffer. You are doing little operations many times over which takes time. You need to do big operations and do them less frequently to improve the speed of your program.