Best way to Pipe InputStream to OutputStream [duplicate]

Question

I was to trying to find the best way to pipe the InputStream to OutputStream. I don't have an option to use any other libraries like Apache IO. Here is the snippet and output.

import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.nio.channels.FileChannel;  public class Pipe {     public static void main(String[] args) throws Exception {          for(PipeTestCase testCase : testCases) {             System.out.println(testCase.getApproach());             InputStream is = new FileInputStream("D:\\in\\lft_.txt");             OutputStream os = new FileOutputStream("D:\\in\\out.txt");              long start = System.currentTimeMillis();                         testCase.pipe(is, os);             long end = System.currentTimeMillis();              System.out.println("Execution Time = " + (end - start) + " millis");             System.out.println("============================================");              is.close();             os.close();         }      }      private static PipeTestCase[] testCases = {          new PipeTestCase("Fixed Buffer Read") {                      @Override             public void pipe(InputStream is, OutputStream os) throws IOException {                 byte[] buffer = new byte[1024];                 while(is.read(buffer) > -1) {                     os.write(buffer);                    }             }         },          new PipeTestCase("dynamic Buffer Read") {                        @Override             public void pipe(InputStream is, OutputStream os) throws IOException {                 byte[] buffer = new byte[is.available()];                 while(is.read(buffer) > -1) {                     os.write(buffer);                        buffer = new byte[is.available() + 1];                 }             }         },          new PipeTestCase("Byte Read") {                      @Override             public void pipe(InputStream is, OutputStream os) throws IOException {                 int c;                  while((c = is.read()) > -1) {                     os.write(c);                     }             }         },           new PipeTestCase("NIO Read") {                       @Override             public void pipe(InputStream is, OutputStream os) throws IOException {                 FileChannel source      = ((FileInputStream) is).getChannel();                  FileChannel destnation  = ((FileOutputStream) os).getChannel();                 destnation.transferFrom(source, 0, source.size());             }         },       }; }   abstract class PipeTestCase {     private String approach;      public PipeTestCase( final String approach) {         this.approach = approach;                }      public String getApproach() {         return approach;     }      public abstract void pipe(InputStream is, OutputStream os) throws IOException; } 

Output (~4MB input file) :

Fixed Buffer Read Execution Time = 71 millis ============================================ dynamic Buffer Read Execution Time = 167 millis ============================================ Byte Read Execution Time = 29124 millis ============================================ NIO Read Execution Time = 125 millis ============================================ 

'Dynamic Buffer Read' uses available() method. But it is not reliable as per java docs

It is never correct to use the return value of this method to allocate a buffer intended to hold all data in this stream.

'Byte Read' seems to be very slow.

So 'Fixed Buffer Read' is the best option for pipe? Any thoughts?

Answer 1

Java 9

Since Java 9 one can use this method from InputStream:

public long transferTo(OutputStream out) throws IOException 

Pre Java 9

A one-liner from apache commons:

IOUtils.copy(inputStream, outputStream); 

Documentation here. There are multiple copy methods with different parameters. It is also possible to specify the buffer size.

Answer 2

I came across this, and the final read can cause problems.

SUGGESTED CHANGE:

public void pipe(InputStream is, OutputStream os) throws IOException {   int n;   byte[] buffer = new byte[1024];   while((n = is.read(buffer)) > -1) {     os.write(buffer, 0, n);   // Don't allow any extra bytes to creep in, final write   }  os.close (); 

I also agree that 16384 is probably a better fixed buffer size than 1024.

IMHO...