Reputation: 118063
I was surprised to find today that I couldn't track down any simple way to write the contents of an InputStream
to an OutputStream
in Java. Obviously, the byte buffer code isn't difficult to write, but I suspect I'm just missing something which would make my life easier (and the code clearer).
So, given an InputStream
in
and an OutputStream
out
, is there a simpler way to write the following?
byte[] buffer = new byte[1024];
int len = in.read(buffer);
while (len != -1) {
out.write(buffer, 0, len);
len = in.read(buffer);
}
Upvotes: 523
Views: 513198
Reputation: 22027
Here comes how I'm doing with a simplest for loop.
private void copy(final InputStream in, final OutputStream out)
throws IOException {
final byte[] b = new byte[8192];
for (int r; (r = in.read(b)) != -1;) {
out.write(b, 0, r);
}
}
Upvotes: 6
Reputation: 1124
Not very readable, but effective, has no dependencies and runs with any java version
byte[] buffer=new byte[1024];
for(int n; (n=inputStream.read(buffer))!=-1; outputStream.write(buffer,0,n));
Upvotes: 2
Reputation: 8691
I used ByteStreamKt.copyTo(src, dst, buffer.length)
method
Here is my code
public static void replaceCurrentDb(Context context, Uri newDbUri) {
try {
File currentDb = context.getDatabasePath(DATABASE_NAME);
if (currentDb.exists()) {
InputStream src = context.getContentResolver().openInputStream(newDbUri);
FileOutputStream dst = new FileOutputStream(currentDb);
final byte[] buffer = new byte[8 * 1024];
ByteStreamsKt.copyTo(src, dst, buffer.length);
src.close();
dst.close();
Toast.makeText(context, "SUCCESS! Your selected file is set as current menu.", Toast.LENGTH_LONG).show();
}
else
Log.e("DOWNLOAD:::: Database", " fail, database not found");
}
catch (IOException e) {
Toast.makeText(context, "Data Download FAIL.", Toast.LENGTH_LONG).show();
Log.e("DOWNLOAD FAIL!!!", "fail, reason:", e);
}
}
Upvotes: 0
Reputation: 19233
The JDK
uses the same code so it seems like there is no "easier" way without clunky third party libraries (which probably don't do anything different anyway). The following is directly copied from java.nio.file.Files.java
:
// buffer size used for reading and writing
private static final int BUFFER_SIZE = 8192;
/**
* Reads all bytes from an input stream and writes them to an output stream.
*/
private static long copy(InputStream source, OutputStream sink) throws IOException {
long nread = 0L;
byte[] buf = new byte[BUFFER_SIZE];
int n;
while ((n = source.read(buf)) > 0) {
sink.write(buf, 0, n);
nread += n;
}
return nread;
}
Upvotes: 23
Reputation: 1751
Using Java7 and try-with-resources, comes with a simplified and readable version.
try(InputStream inputStream = new FileInputStream("C:\\mov.mp4");
OutputStream outputStream = new FileOutputStream("D:\\mov.mp4")) {
byte[] buffer = new byte[10*1024];
for (int length; (length = inputStream.read(buffer)) != -1; ) {
outputStream.write(buffer, 0, length);
}
} catch (FileNotFoundException exception) {
exception.printStackTrace();
} catch (IOException ioException) {
ioException.printStackTrace();
}
Upvotes: 8
Reputation: 13679
This is my best shot!!
And do not use inputStream.transferTo(...)
because is too generic.
Your code performance will be better if you control your buffer memory.
public static void transfer(InputStream in, OutputStream out, int buffer) throws IOException {
byte[] read = new byte[buffer]; // Your buffer size.
while (0 < (buffer = in.read(read)))
out.write(read, 0, buffer);
}
I use it with this (improvable) method when I know in advance the size of the stream.
public static void transfer(int size, InputStream in, OutputStream out) throws IOException {
transfer(in, out,
size > 0xFFFF ? 0xFFFF // 16bits 65,536
: size > 0xFFF ? 0xFFF// 12bits 4096
: size < 0xFF ? 0xFF // 8bits 256
: size
);
}
Upvotes: 3
Reputation: 41662
I use BufferedInputStream
and BufferedOutputStream
to remove the buffering semantics from the code
try (OutputStream out = new BufferedOutputStream(...);
InputStream in = new BufferedInputStream(...))) {
int ch;
while ((ch = in.read()) != -1) {
out.write(ch);
}
}
Upvotes: 4
Reputation: 27737
Using Guava's ByteStreams.copy()
:
ByteStreams.copy(inputStream, outputStream);
Upvotes: 62
Reputation: 48193
Since Java 9, InputStream
provides a method called transferTo
with the following signature:
public long transferTo(OutputStream out) throws IOException
As the documentation states, transferTo
will:
Reads all bytes from this input stream and writes the bytes to the given output stream in the order that they are read. On return, this input stream will be at end of stream. This method does not close either stream.
This method may block indefinitely reading from the input stream, or writing to the output stream. The behavior for the case where the input and/or output stream is asynchronously closed, or the thread interrupted during the transfer, is highly input and output stream specific, and therefore not specified
So in order to write contents of a Java InputStream
to an OutputStream
, you can write:
input.transferTo(output);
Upvotes: 268
Reputation: 105193
Try Cactoos:
new LengthOf(new TeeInput(input, output)).value();
More details here: http://www.yegor256.com/2017/06/22/object-oriented-input-output-in-cactoos.html
Upvotes: -1
Reputation: 16644
For those who use Spring framework there is a useful StreamUtils class:
StreamUtils.copy(in, out);
The above does not close the streams. If you want the streams closed after the copy, use FileCopyUtils class instead:
FileCopyUtils.copy(in, out);
Upvotes: 21
Reputation: 425328
A IMHO more minimal snippet (that also more narrowly scopes the length variable):
byte[] buffer = new byte[2048];
for (int n = in.read(buffer); n >= 0; n = in.read(buffer))
out.write(buffer, 0, n);
As a side note, I don't understand why more people don't use a for
loop, instead opting for a while
with an assign-and-test expression that is regarded by some as "poor" style.
Upvotes: 3
Reputation: 9398
If you are using Java 7, Files (in the standard library) is the best approach:
/* You can get Path from file also: file.toPath() */
Files.copy(InputStream in, Path target)
Files.copy(Path source, OutputStream out)
Edit: Of course it's just useful when you create one of InputStream or OutputStream from file. Use file.toPath()
to get path from file.
To write into an existing file (e.g. one created with File.createTempFile()
), you'll need to pass the REPLACE_EXISTING
copy option (otherwise FileAlreadyExistsException
is thrown):
Files.copy(in, target, StandardCopyOption.REPLACE_EXISTING)
Upvotes: 350
Reputation: 13374
PipedInputStream
and PipedOutputStream
should only be used when you have multiple threads, as noted by the Javadoc.
Also, note that input streams and output streams do not wrap any thread interruptions with IOException
s... So, you should consider incorporating an interruption policy to your code:
byte[] buffer = new byte[1024];
int len = in.read(buffer);
while (len != -1) {
out.write(buffer, 0, len);
len = in.read(buffer);
if (Thread.interrupted()) {
throw new InterruptedException();
}
}
This would be an useful addition if you expect to use this API for copying large volumes of data, or data from streams that get stuck for an intolerably long time.
Upvotes: 19
Reputation: 45
public static boolean copyFile(InputStream inputStream, OutputStream out) {
byte buf[] = new byte[1024];
int len;
long startTime=System.currentTimeMillis();
try {
while ((len = inputStream.read(buf)) != -1) {
out.write(buf, 0, len);
}
long endTime=System.currentTimeMillis()-startTime;
Log.v("","Time taken to transfer all bytes is : "+endTime);
out.close();
inputStream.close();
} catch (IOException e) {
return false;
}
return true;
}
Upvotes: -1
Reputation: 1118
If you only need this for writing an InputStream
to a File
then you can use this simple function:
private void copyInputStreamToFile( InputStream in, File file ) {
try {
OutputStream out = new FileOutputStream(file);
byte[] buf = new byte[1024];
int len;
while((len=in.read(buf))>0){
out.write(buf,0,len);
}
out.close();
in.close();
} catch (Exception e) {
e.printStackTrace();
}
}
Upvotes: 31
Reputation: 16905
As WMR mentioned, org.apache.commons.io.IOUtils
from Apache has a method called copy(InputStream,OutputStream)
which does exactly what you're looking for.
So, you have:
InputStream in;
OutputStream out;
IOUtils.copy(in,out);
in.close();
out.close();
...in your code.
Is there a reason you're avoiding IOUtils
?
Upvotes: 414
Reputation: 4250
you can use this method
public static void copyStream(InputStream is, OutputStream os)
{
final int buffer_size=1024;
try
{
byte[] bytes=new byte[buffer_size];
for(;;)
{
int count=is.read(bytes, 0, buffer_size);
if(count==-1)
break;
os.write(bytes, 0, count);
}
}
catch(Exception ex){}
}
Upvotes: -7
Reputation: 19822
Use Commons Net's Util class:
import org.apache.commons.net.io.Util;
...
Util.copyStream(in, out);
Upvotes: 4
Reputation: 8407
I think it's better to use a large buffer, because most of the files are greater than 1024 bytes. Also it's a good practice to check the number of read bytes to be positive.
byte[] buffer = new byte[4096];
int n;
while ((n = in.read(buffer)) > 0) {
out.write(buffer, 0, n);
}
out.close();
Upvotes: 2
Reputation: 36940
Another possible candidate are the Guava I/O utilities:
http://code.google.com/p/guava-libraries/wiki/IOExplained
I thought I'd use these since Guava is already immensely useful in my project, rather than adding yet another library for one function.
Upvotes: 0
Reputation: 12971
There's no way to do this a lot easier with JDK methods, but as Apocalisp has already noted, you're not the only one with this idea: You could use IOUtils from Jakarta Commons IO, it also has a lot of other useful things, that IMO should actually be part of the JDK...
Upvotes: 8
Reputation: 525
PipedInputStream and PipedOutputStream may be of some use, as you can connect one to the other.
Upvotes: 0
Reputation: 44613
I think this will work, but make sure to test it... minor "improvement", but it might be a bit of a cost at readability.
byte[] buffer = new byte[1024];
int len;
while ((len = in.read(buffer)) != -1) {
out.write(buffer, 0, len);
}
Upvotes: 110