Writing Arrays of Bytes
It’s often faster to write larger chunks of
data than to write
byte by byte. Two overloaded variants of
the write()
method do this:
public void write(byte[] data) throws IOException public void write(byte[] data, int offset, int length) throws IOException
The first variant writes the entire byte
array
data
. The second writes only the sub-array of
data
starting at offset
and
continuing for length
bytes. For example, the
following code fragment blasts the bytes in a string onto
System.out
:
String s = "How are streams treating you?"; byte[] data = s.getBytes(); System.out.write(data);
Conversely, you may run into performance problems if you attempt to write too much data at a time. The exact turnaround point depends on the eventual destination of the data. Files are often best written in small multiples of the block size of the disk, typically 512, 1024, or 2048 bytes. Network connections often require smaller buffer sizes, 128 or 256 bytes. The optimal buffer size depends on too many system-specific details for anything to be guaranteed, but I often use 128 bytes for network connections and 1024 bytes for files.
Example 2.2 is a simple program that constructs a
byte array filled with an ASCII chart, then blasts it onto the
console in one call to write()
.
Example 2-2. The AsciiArray Program
import java.io.*; public class AsciiArray { public static void main(String[] args) { byte[] b = new byte[(127-31)*2]; int index = 0; for (int i = 32; i < 127; i++) { b[index++] ...
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