public class IOUtils extends Object
This class provides static utility methods for input/output operations.
The byte-to-char methods and char-to-byte methods involve a conversion step. Two methods are provided in each case, one that uses the platform default encoding and the other which allows you to specify an encoding. You are encouraged to always specify an encoding because relying on the platform default can lead to unexpected results, for example when moving from development to production.
All the methods in this class that read a stream are buffered internally.
This means that there is no cause to use a BufferedInputStream
or BufferedReader. The default buffer size of 4K has been shown
to be efficient in tests.
Wherever possible, the methods in this class do not flush or close the stream. This is to avoid making non-portable assumptions about the streams' origin and further use. Thus the caller is still responsible for closing streams after use.
Origin of code: Excalibur.
| Constructor and Description |
|---|
IOUtils()
Instances should NOT be constructed in standard programming.
|
| Modifier and Type | Method and Description |
|---|---|
static void |
closeQuietly(Closeable closeable)
Closes a
Closeable unconditionally. |
static int |
copy(InputStream input,
OutputStream output)
Copies bytes from an
InputStream to an
OutputStream. |
static long |
copyLarge(InputStream input,
OutputStream output)
Copies bytes from a large (over 2GB)
InputStream to an
OutputStream. |
static int |
read(InputStream input,
byte[] buffer,
int offset,
int length)
Reads bytes from an input stream.
|
static void |
readFully(InputStream input,
byte[] buffer)
Reads the requested number of bytes or fail if there are not enough left.
|
static void |
readFully(InputStream input,
byte[] buffer,
int offset,
int length)
Reads the requested number of bytes or fail if there are not enough left.
|
public IOUtils()
public static void closeQuietly(Closeable closeable)
Closeable unconditionally.
Equivalent to Closeable.close(), except any exceptions will be ignored. This is typically used in
finally blocks.
Example code:
Closeable closeable = null;
try {
closeable = new FileReader("foo.txt");
// process closeable
closeable.close();
} catch (Exception e) {
// error handling
} finally {
IOUtils.closeQuietly(closeable);
}
Closing all streams:
try {
return IOUtils.copy(inputStream, outputStream);
} finally {
IOUtils.closeQuietly(inputStream);
IOUtils.closeQuietly(outputStream);
}
closeable - the objects to close, may be null or already closedpublic static int copy(InputStream input, OutputStream output) throws IOException
InputStream to an
OutputStream.
This method buffers the input internally, so there is no need to use a
BufferedInputStream.
Large streams (over 2GB) will return a bytes copied value of
-1 after the copy has completed since the correct
number of bytes cannot be returned as an int. For large streams
use the copyLarge(InputStream, OutputStream) method.
input - the InputStream to read fromoutput - the OutputStream to write toNullPointerException - if the input or output is nullIOException - if an I/O error occurspublic static long copyLarge(InputStream input, OutputStream output) throws IOException
InputStream to an
OutputStream.
This method buffers the input internally, so there is no need to use a
BufferedInputStream.
The buffer size is given by DEFAULT_BUFFER_SIZE.
input - the InputStream to read fromoutput - the OutputStream to write toNullPointerException - if the input or output is nullIOException - if an I/O error occurspublic static int read(InputStream input, byte[] buffer, int offset, int length) throws IOException
InputStream.input - where to read input frombuffer - destinationoffset - initial offset into bufferlength - length to read, must be >= 0IOException - if a read error occurspublic static void readFully(InputStream input, byte[] buffer, int offset, int length) throws IOException
This allows for the possibility that InputStream.read(byte[], int, int) may
not read as many bytes as requested (most likely because of reaching EOF).
input - where to read input frombuffer - destinationoffset - initial offset into bufferlength - length to read, must be >= 0IOException - if there is a problem reading the fileIllegalArgumentException - if length is negativeEOFException - if the number of bytes read was incorrectpublic static void readFully(InputStream input, byte[] buffer) throws IOException
This allows for the possibility that InputStream.read(byte[], int, int) may
not read as many bytes as requested (most likely because of reaching EOF).
input - where to read input frombuffer - destinationIOException - if there is a problem reading the fileIllegalArgumentException - if length is negativeEOFException - if the number of bytes read was incorrectCopyright © 2000-2021 Apache Software Foundation. All Rights Reserved.