Class IOUtils
This class provides static utility methods for input/output operations.
- closeQuietly - these methods close a stream ignoring nulls and exceptions
- toXxx/read - these methods read data from a stream
- write - these methods write data to a stream
- copy - these methods copy all the data from one stream to another
- contentEquals - these methods compare the content of two streams
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.
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Field SummaryFields
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Constructor SummaryConstructors
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Method SummaryModifier and TypeMethodDescriptionstatic voidcloseQuietly(Closeable closeable) Closes aCloseableunconditionally.static intcopy(InputStream input, OutputStream output) Copies bytes from anInputStreamto anOutputStream.static longcopyLarge(InputStream input, OutputStream output) Copies bytes from a large (over 2GB)InputStreamto anOutputStream.static intread(InputStream input, byte[] buffer, int offset, int length) Reads bytes from an input stream.static voidreadFully(InputStream input, byte[] buffer) Reads the requested number of bytes or fail if there are not enough left.static voidreadFully(InputStream input, byte[] buffer, int offset, int length) Reads the requested number of bytes or fail if there are not enough left.
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Field Details- 
EOFpublic static final int EOFRepresents the end-of-file (or stream).- Since:
- 2.5 (made public)
- See Also:
 
 
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Constructor Details- 
IOUtilspublic IOUtils()
 
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Method Details- 
closeQuietlyCloses aCloseableunconditionally.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); }- Parameters:
- closeable- the objects to close, may be null or already closed
- Since:
- 2.0
 
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copyCopies bytes from anInputStreamto anOutputStream.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 -1after the copy has completed since the correct number of bytes cannot be returned as an int. For large streams use thecopyLarge(InputStream, OutputStream)method.- Parameters:
- input- the- InputStreamto read from
- output- the- OutputStreamto write to
- Returns:
- the number of bytes copied, or -1 if > Integer.MAX_VALUE
- Throws:
- NullPointerException- if the input or output is null
- IOException- if an I/O error occurs
- Since:
- 1.1
 
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copyLargeCopies bytes from a large (over 2GB)InputStreamto anOutputStream.This method buffers the input internally, so there is no need to use a BufferedInputStream.The buffer size is given by DEFAULT_BUFFER_SIZE.- Parameters:
- input- the- InputStreamto read from
- output- the- OutputStreamto write to
- Returns:
- the number of bytes copied
- Throws:
- NullPointerException- if the input or output is null
- IOException- if an I/O error occurs
- Since:
- 1.3
 
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readReads bytes from an input stream. This implementation guarantees that it will read as many bytes as possible before giving up; this may not always be the case for subclasses ofInputStream.- Parameters:
- input- where to read input from
- buffer- destination
- offset- initial offset into buffer
- length- length to read, must be >= 0
- Returns:
- actual length read; may be less than requested if EOF was reached
- Throws:
- IOException- if a read error occurs
- Since:
- 2.2
 
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readFullypublic static void readFully(InputStream input, byte[] buffer, int offset, int length) throws IOException Reads the requested number of bytes or fail if there are not enough left.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).- Parameters:
- input- where to read input from
- buffer- destination
- offset- initial offset into buffer
- length- length to read, must be >= 0
- Throws:
- IOException- if there is a problem reading the file
- IllegalArgumentException- if length is negative
- EOFException- if the number of bytes read was incorrect
- Since:
- 2.2
 
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readFullyReads the requested number of bytes or fail if there are not enough left.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).- Parameters:
- input- where to read input from
- buffer- destination
- Throws:
- IOException- if there is a problem reading the file
- IllegalArgumentException- if length is negative
- EOFException- if the number of bytes read was incorrect
- Since:
- 2.2
 
 
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