Class IOUtil
- java.lang.Object
-
- org.apache.maven.shared.utils.io.IOUtil
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public final class IOUtil extends java.lang.Object
General IO Stream manipulation.This class provides static utility methods for input/output operations, particularly buffered copying between sources (
InputStream
,Reader
,String
andbyte[]
) and destinations (OutputStream
,Writer
,String
andbyte[]
).Unless otherwise noted, these
copy
methods do not flush or close the streams. Often, doing so would require making non-portable assumptions about the streams' origin and further use. This means that both streams'close()
methods must be called after copying. if one omits this step, then the stream resources (sockets, file descriptors) are released when the associated Stream is garbage-collected. It is not a good idea to rely on this mechanism. For a good overview of the distinction between "memory management" and "resource management", see this UnixReview articleFor each
copy
method, a variant is provided that allows the caller to specify the buffer size (the default is 4k). As the buffer size can have a fairly large impact on speed, this may be worth tweaking. Often "large buffer -> faster" does not hold, even for large data transfers.For byte-to-char methods, a
copy
variant allows the encoding to be selected (otherwise the platform default is used).The
copy
methods use an internal buffer when copying. It is therefore advisable not to deliberately wrap the stream arguments to thecopy
methods inBuffered*
streams. For example, don't do the following:copy( new BufferedInputStream( in ), new BufferedOutputStream( out ) );
The rationale is as follows:
Imagine that an InputStream's read() is a very expensive operation, which would usually suggest wrapping in a BufferedInputStream. The BufferedInputStream works by issuing infrequent
InputStream.read(byte[] b, int off, int len)
requests on the underlying InputStream, to fill an internal buffer, from which furtherread
requests can inexpensively get their data (until the buffer runs out).However, the
copy
methods do the same thing, keeping an internal buffer, populated byInputStream.read(byte[] b, int off, int len)
requests. Having two buffers (or three if the destination stream is also buffered) is pointless, and the unnecessary buffer management hurts performance slightly (about 3%, according to some simple experiments).- Version:
- CVS $Revision$ $Date$
-
-
Field Summary
Fields Modifier and Type Field Description private static int
DEFAULT_BUFFER_SIZE
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Constructor Summary
Constructors Modifier Constructor Description private
IOUtil()
Private constructor to prevent instantiation.
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method Description static void
close(java.io.InputStream inputStream)
Closes anInputStream
suppressing anyIOException
.static void
close(java.io.OutputStream outputStream)
Closes anOutputStream
suppressing anyIOException
.static void
close(java.io.Reader reader)
Closes aReader
suppressing anyIOException
.static void
close(java.io.Writer writer)
Closes aWriter
suppressing anyIOException
.static void
close(java.nio.channels.Channel channel)
Closes aChannel
suppressing anyIOException
.static boolean
contentEquals(java.io.InputStream input1, java.io.InputStream input2)
Compare the contents of two Streams to determine if they are equal or not.static void
copy(byte[] input, java.io.OutputStream output)
Copy bytes from abyte[]
to anOutputStream
.static void
copy(byte[] input, java.io.Writer output)
Copy and convert bytes from abyte[]
to chars on aWriter
.static void
copy(byte[] input, java.io.Writer output, int bufferSize)
Copy and convert bytes from abyte[]
to chars on aWriter
.static void
copy(byte[] input, java.io.Writer output, java.lang.String encoding)
Copy and convert bytes from abyte[]
to chars on aWriter
, using the specified encoding.static void
copy(byte[] input, java.io.Writer output, java.lang.String encoding, int bufferSize)
Copy and convert bytes from abyte[]
to chars on aWriter
, using the specified encoding.static void
copy(java.io.InputStream input, java.io.OutputStream output)
Copy bytes from anInputStream
to anOutputStream
.static void
copy(java.io.InputStream input, java.io.OutputStream output, int bufferSize)
Copy bytes from anInputStream
to anOutputStream
.static void
copy(java.io.InputStream input, java.io.Writer output)
Copy and convert bytes from anInputStream
to chars on aWriter
.static void
copy(java.io.InputStream input, java.io.Writer output, int bufferSize)
Copy and convert bytes from anInputStream
to chars on aWriter
.static void
copy(java.io.InputStream input, java.io.Writer output, java.lang.String encoding)
Copy and convert bytes from anInputStream
to chars on aWriter
, using the specified encoding.static void
copy(java.io.InputStream input, java.io.Writer output, java.lang.String encoding, int bufferSize)
Copy and convert bytes from anInputStream
to chars on aWriter
, using the specified encoding.static void
copy(java.io.Reader input, java.io.OutputStream output)
Serialize chars from aReader
to bytes on anOutputStream
, and flush theOutputStream
.static void
copy(java.io.Reader input, java.io.OutputStream output, int bufferSize)
Serialize chars from aReader
to bytes on anOutputStream
, and flush theOutputStream
.static void
copy(java.io.Reader input, java.io.Writer output)
Copy chars from aReader
to aWriter
.static void
copy(java.io.Reader input, java.io.Writer output, int bufferSize)
Copy chars from aReader
to aWriter
.static void
copy(java.lang.String input, java.io.OutputStream output)
Serialize chars from aString
to bytes on anOutputStream
, and flush theOutputStream
.static void
copy(java.lang.String input, java.io.OutputStream output, int bufferSize)
Serialize chars from aString
to bytes on anOutputStream
, and flush theOutputStream
.static void
copy(java.lang.String input, java.io.Writer output)
Copy chars from aString
to aWriter
.static byte[]
toByteArray(java.io.InputStream input)
Get the contents of anInputStream
as abyte[]
.static byte[]
toByteArray(java.io.InputStream input, int bufferSize)
Get the contents of anInputStream
as abyte[]
.static byte[]
toByteArray(java.io.Reader input)
Get the contents of aReader
as abyte[]
.static byte[]
toByteArray(java.io.Reader input, int bufferSize)
Get the contents of aReader
as abyte[]
.static byte[]
toByteArray(java.lang.String input)
Get the contents of aString
as abyte[]
.static byte[]
toByteArray(java.lang.String input, int bufferSize)
Get the contents of aString
as abyte[]
.static java.lang.String
toString(byte[] input)
Get the contents of abyte[]
as a String.static java.lang.String
toString(byte[] input, int bufferSize)
Get the contents of abyte[]
as a String.static java.lang.String
toString(byte[] input, java.lang.String encoding)
Get the contents of abyte[]
as a String.static java.lang.String
toString(byte[] input, java.lang.String encoding, int bufferSize)
Get the contents of abyte[]
as a String.static java.lang.String
toString(java.io.InputStream input)
Get the contents of anInputStream
as a String.static java.lang.String
toString(java.io.InputStream input, int bufferSize)
Get the contents of anInputStream
as a String.static java.lang.String
toString(java.io.InputStream input, java.lang.String encoding)
Get the contents of anInputStream
as a String.static java.lang.String
toString(java.io.InputStream input, java.lang.String encoding, int bufferSize)
Get the contents of anInputStream
as a String.static java.lang.String
toString(java.io.Reader input)
Get the contents of aReader
as a String.static java.lang.String
toString(java.io.Reader input, int bufferSize)
Get the contents of aReader
as a String.
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Field Detail
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DEFAULT_BUFFER_SIZE
private static final int DEFAULT_BUFFER_SIZE
- See Also:
- Constant Field Values
-
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Method Detail
-
copy
public static void copy(@Nonnull java.io.InputStream input, @Nonnull java.io.OutputStream output) throws java.io.IOException
Copy bytes from anInputStream
to anOutputStream
.- Parameters:
input
- The input size.output
- The resulting output.- Throws:
java.io.IOException
- in case of an error.
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copy
public static void copy(@Nonnull java.io.InputStream input, @Nonnull java.io.OutputStream output, int bufferSize) throws java.io.IOException
Copy bytes from anInputStream
to anOutputStream
.- Parameters:
input
- The input size.output
- The resulting output.bufferSize
- Size of internal buffer to use.- Throws:
java.io.IOException
- in case of an error.
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copy
public static void copy(@Nonnull java.io.Reader input, @Nonnull java.io.Writer output) throws java.io.IOException
Copy chars from aReader
to aWriter
.- Parameters:
input
- The input size.output
- The resulting output.- Throws:
java.io.IOException
- in case of failure.
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copy
public static void copy(@Nonnull java.io.Reader input, @Nonnull java.io.Writer output, int bufferSize) throws java.io.IOException
Copy chars from aReader
to aWriter
.- Parameters:
input
- The input size.output
- The resulting output.bufferSize
- Size of internal buffer to use.- Throws:
java.io.IOException
- in case of failure.
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copy
public static void copy(@Nonnull java.io.InputStream input, @Nonnull java.io.Writer output) throws java.io.IOException
Copy and convert bytes from anInputStream
to chars on aWriter
. The platform's default encoding is used for the byte-to-char conversion.- Parameters:
input
- The input size.output
- The resulting output.- Throws:
java.io.IOException
- in case of failure.
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copy
public static void copy(@Nonnull java.io.InputStream input, @Nonnull java.io.Writer output, int bufferSize) throws java.io.IOException
Copy and convert bytes from anInputStream
to chars on aWriter
. The platform's default encoding is used for the byte-to-char conversion.- Parameters:
input
- The input size.output
- The resulting output.bufferSize
- Size of internal buffer to use.- Throws:
java.io.IOException
- in case of failure.
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copy
public static void copy(@Nonnull java.io.InputStream input, @Nonnull java.io.Writer output, @Nonnull java.lang.String encoding) throws java.io.IOException
Copy and convert bytes from anInputStream
to chars on aWriter
, using the specified encoding.- Parameters:
input
- The input size.output
- The resulting output.encoding
- The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.- Throws:
java.io.IOException
- in case of failure.
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copy
public static void copy(@Nonnull java.io.InputStream input, @Nonnull java.io.Writer output, @Nonnull java.lang.String encoding, int bufferSize) throws java.io.IOException
Copy and convert bytes from anInputStream
to chars on aWriter
, using the specified encoding.- Parameters:
encoding
- The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.input
- The input size.output
- The resulting output.bufferSize
- Size of internal buffer to use.- Throws:
java.io.IOException
- in case of failure.
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toString
@Nonnull public static java.lang.String toString(@Nonnull java.io.InputStream input) throws java.io.IOException
Get the contents of anInputStream
as a String. The platform's default encoding is used for the byte-to-char conversion.- Parameters:
input
- The input size.- Returns:
- The resulting string.
- Throws:
java.io.IOException
- in case of failure.
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toString
@Nonnull public static java.lang.String toString(@Nonnull java.io.InputStream input, int bufferSize) throws java.io.IOException
Get the contents of anInputStream
as a String. The platform's default encoding is used for the byte-to-char conversion.- Parameters:
input
- The input size.bufferSize
- Size of internal buffer to use.- Returns:
- the resulting string.
- Throws:
java.io.IOException
- in case of failure.
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toString
@Nonnull public static java.lang.String toString(@Nonnull java.io.InputStream input, @Nonnull java.lang.String encoding) throws java.io.IOException
Get the contents of anInputStream
as a String.- Parameters:
input
- The input size.encoding
- The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.- Returns:
- the converted string.
- Throws:
java.io.IOException
- in case of failure.
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toString
@Nonnull public static java.lang.String toString(@Nonnull java.io.InputStream input, @Nonnull java.lang.String encoding, int bufferSize) throws java.io.IOException
Get the contents of anInputStream
as a String.- Parameters:
input
- The input size.encoding
- The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.bufferSize
- Size of internal buffer to use.- Returns:
- The converted string.
- Throws:
java.io.IOException
- in case of failure.
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toByteArray
@Nonnull public static byte[] toByteArray(@Nonnull java.io.InputStream input) throws java.io.IOException
Get the contents of anInputStream
as abyte[]
.- Parameters:
input
- The input size.- Returns:
- the resulting byte array.
- Throws:
java.io.IOException
- in case of failure.
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toByteArray
@Nonnull public static byte[] toByteArray(@Nonnull java.io.InputStream input, int bufferSize) throws java.io.IOException
Get the contents of anInputStream
as abyte[]
.- Parameters:
input
- The input size.bufferSize
- Size of internal buffer to use.- Returns:
- the resulting byte array.
- Throws:
java.io.IOException
- in case of failure.
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copy
public static void copy(@Nonnull java.io.Reader input, @Nonnull java.io.OutputStream output) throws java.io.IOException
Serialize chars from aReader
to bytes on anOutputStream
, and flush theOutputStream
.- Parameters:
input
- The input size.output
- The resulting output.- Throws:
java.io.IOException
- in case of failure.
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copy
public static void copy(@Nonnull java.io.Reader input, @Nonnull java.io.OutputStream output, int bufferSize) throws java.io.IOException
Serialize chars from aReader
to bytes on anOutputStream
, and flush theOutputStream
.- Parameters:
input
- The input size.output
- The resulting output.bufferSize
- Size of internal buffer to use.- Throws:
java.io.IOException
- in case of failure.
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toString
@Nonnull public static java.lang.String toString(@Nonnull java.io.Reader input) throws java.io.IOException
Get the contents of aReader
as a String.- Parameters:
input
- The input size.- Returns:
- The converted string.
- Throws:
java.io.IOException
- in case of failure.
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toString
@Nonnull public static java.lang.String toString(@Nonnull java.io.Reader input, int bufferSize) throws java.io.IOException
Get the contents of aReader
as a String.- Parameters:
input
- The input size.bufferSize
- Size of internal buffer to use.- Returns:
- the resulting byte array.
- Throws:
java.io.IOException
- in case of failure.
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toByteArray
@Nonnull public static byte[] toByteArray(@Nonnull java.io.Reader input) throws java.io.IOException
Get the contents of aReader
as abyte[]
.- Parameters:
input
- The input size.- Returns:
- the resulting byte array.
- Throws:
java.io.IOException
- in case of failure.
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toByteArray
@Nonnull public static byte[] toByteArray(@Nonnull java.io.Reader input, int bufferSize) throws java.io.IOException
Get the contents of aReader
as abyte[]
.- Parameters:
input
- The input size.bufferSize
- Size of internal buffer to use.- Returns:
- the resulting byte array.
- Throws:
java.io.IOException
- in case of failure.
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copy
public static void copy(@Nonnull java.lang.String input, @Nonnull java.io.OutputStream output) throws java.io.IOException
Serialize chars from aString
to bytes on anOutputStream
, and flush theOutputStream
.- Parameters:
input
- The input size.output
- The resulting output.- Throws:
java.io.IOException
- in case of failure.
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copy
public static void copy(@Nonnull java.lang.String input, @Nonnull java.io.OutputStream output, int bufferSize) throws java.io.IOException
Serialize chars from aString
to bytes on anOutputStream
, and flush theOutputStream
.- Parameters:
input
- The input size.output
- The resulting output.bufferSize
- Size of internal buffer to use.- Throws:
java.io.IOException
- in case of failure.
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copy
public static void copy(@Nonnull java.lang.String input, @Nonnull java.io.Writer output) throws java.io.IOException
Copy chars from aString
to aWriter
.- Parameters:
input
- Input string.output
- resulting outputWriter
- Throws:
java.io.IOException
- in case of failure.
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toByteArray
@Nonnull public static byte[] toByteArray(@Nonnull java.lang.String input) throws java.io.IOException
Get the contents of aString
as abyte[]
.- Parameters:
input
- The input size.- Returns:
- The resulting byte array.
- Throws:
java.io.IOException
- in case of failure.
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toByteArray
@Nonnull public static byte[] toByteArray(@Nonnull java.lang.String input, int bufferSize) throws java.io.IOException
Get the contents of aString
as abyte[]
.- Parameters:
input
- The input size.bufferSize
- Size of internal buffer to use.- Returns:
- The resulting byte array.
- Throws:
java.io.IOException
- in case of failure.
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copy
public static void copy(@Nonnull byte[] input, @Nonnull java.io.Writer output) throws java.io.IOException
Copy and convert bytes from abyte[]
to chars on aWriter
. The platform's default encoding is used for the byte-to-char conversion.- Parameters:
input
- The input size.output
- The resulting output.- Throws:
java.io.IOException
- in case of failure.
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copy
public static void copy(@Nonnull byte[] input, @Nonnull java.io.Writer output, int bufferSize) throws java.io.IOException
Copy and convert bytes from abyte[]
to chars on aWriter
. The platform's default encoding is used for the byte-to-char conversion.- Parameters:
input
- The input size.output
- The resulting output.bufferSize
- Size of internal buffer to use.- Throws:
java.io.IOException
- in case of failure.
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copy
public static void copy(@Nonnull byte[] input, @Nonnull java.io.Writer output, java.lang.String encoding) throws java.io.IOException
Copy and convert bytes from abyte[]
to chars on aWriter
, using the specified encoding.- Parameters:
encoding
- The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.input
- The input size.output
- The resulting output.- Throws:
java.io.IOException
- in case of failure.
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copy
public static void copy(@Nonnull byte[] input, @Nonnull java.io.Writer output, @Nonnull java.lang.String encoding, int bufferSize) throws java.io.IOException
Copy and convert bytes from abyte[]
to chars on aWriter
, using the specified encoding.- Parameters:
encoding
- The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.input
- The input bytes.output
- The output bufferWriter
bufferSize
- Size of internal buffer to use.- Throws:
java.io.IOException
- in case of failure.
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toString
@Nonnull public static java.lang.String toString(@Nonnull byte[] input) throws java.io.IOException
Get the contents of abyte[]
as a String. The platform's default encoding is used for the byte-to-char conversion.- Parameters:
input
- The input bytes.- Returns:
- The resulting string.
- Throws:
java.io.IOException
- in case of failure.
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toString
@Nonnull public static java.lang.String toString(@Nonnull byte[] input, int bufferSize) throws java.io.IOException
Get the contents of abyte[]
as a String. The platform's default encoding is used for the byte-to-char conversion.- Parameters:
bufferSize
- Size of internal buffer to use.input
- The input bytes.- Returns:
- The created string.
- Throws:
java.io.IOException
- in case of failure.
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toString
@Nonnull public static java.lang.String toString(@Nonnull byte[] input, @Nonnull java.lang.String encoding) throws java.io.IOException
Get the contents of abyte[]
as a String.- Parameters:
encoding
- The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.input
- The input bytes.- Returns:
- The resulting string.
- Throws:
java.io.IOException
- in case of failure.
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toString
@Nonnull public static java.lang.String toString(@Nonnull byte[] input, @Nonnull java.lang.String encoding, int bufferSize) throws java.io.IOException
Get the contents of abyte[]
as a String.- Parameters:
encoding
- The name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.bufferSize
- Size of internal buffer to use.input
- Input bytes.- Returns:
- The resulting string.
- Throws:
java.io.IOException
- in case of failure.
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copy
public static void copy(@Nonnull byte[] input, @Nonnull java.io.OutputStream output) throws java.io.IOException
Copy bytes from abyte[]
to anOutputStream
.- Parameters:
input
- Input byte array.output
- output streamOutputStream
- Throws:
java.io.IOException
- in case of failure.
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contentEquals
public static boolean contentEquals(@Nonnull java.io.InputStream input1, @Nonnull java.io.InputStream input2) throws java.io.IOException
Compare the contents of two Streams to determine if they are equal or not.- Parameters:
input1
- the first streaminput2
- the second stream- Returns:
- true if the content of the streams are equal or they both don't exist, false otherwise
- Throws:
java.io.IOException
- in case of failure.
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close
public static void close(@Nullable java.nio.channels.Channel channel)
Closes aChannel
suppressing anyIOException
.Note:
The usecase justifying this method is a shortcoming of the Java language up to but not including Java 7. For any code targetting Java 7 or later use of this method is highly discouraged and thetry-with-resources
statement should be used instead. Care must be taken to not use this method in a wayIOException
s get suppressed incorrectly. You must close all resources in use inside thetry
block to not suppress exceptions in thefinally
block incorrectly by using this method.Example:
// Introduce variables for the resources and initialize them to null. This cannot throw an exception. Closeable resource1 = null; Closeable resource2 = null; try { // Obtain a resource object and assign it to variable resource1. This may throw an exception. // If successful, resource1 != null. resource1 = ... // Obtain a resource object and assign it to variable resource2. This may throw an exception. // If successful, resource2 != null. Not reached if an exception has been thrown above. resource2 = ... // Perform operations on the resources. This may throw an exception. Not reached if an exception has been // thrown above. Note: Treat the variables resource1 and resource2 the same way as if they would have been // declared with the final modifier - that is - do NOT write anyting like resource1 = something else or // resource2 = something else here. resource1 ... resource2 ... // Finally, close the resources and set the variables to null indicating successful completion. // This may throw an exception. Not reached if an exception has been thrown above. resource1.close(); resource1 = null; // Not reached if an exception has been thrown above. resource2.close(); resource2 = null; // All resources are closed at this point and all operations (up to here) completed successfully without // throwing an exception we would need to handle (by letting it propagate or by catching and handling it). } finally { // Cleanup any resource not closed in the try block due to an exception having been thrown and suppress any // exception this may produce to not stop the exception from the try block to be propagated. If the try // block completed successfully, all variables will have been set to null there and this will not do // anything. This is just to cleanup properly in case of an exception. IOUtil.close( resource1 ); IOUtil.close( resource2 ); // Without that utility method you would need to write the following: // // try // { // if ( resource1 != null ) // { // resource1.close(); // } // } // catch( IOException e ) // { // Suppressed. If resource1 != null, an exception has already been thrown in the try block we need to // propagate instead of this one. // } // finally // { // try // { // if ( resource2 != null ) // { // resource2.close(); // } // } // catch ( IOException e ) // { // Suppressed. If resource2 != null, an exception has already been thrown in the try block we need to // propagate instead of this one. // } // } }
- Parameters:
channel
- The channel to close ornull
.
-
close
public static void close(@Nullable java.io.InputStream inputStream)
Closes anInputStream
suppressing anyIOException
.Note:
The usecase justifying this method is a shortcoming of the Java language up to but not including Java 7. For any code targeting Java 7 or later use of this method is highly discouraged and thetry-with-resources
statement should be used instead. Care must be taken to not use this method in a wayIOException
s get suppressed incorrectly. You must close all resources in use inside thetry
block to not suppress exceptions in thefinally
block incorrectly by using this method.Example:
// Introduce variables for the resources and initialize them to null. This cannot throw an exception. Closeable resource1 = null; Closeable resource2 = null; try { // Obtain a resource object and assign it to variable resource1. This may throw an exception. // If successful, resource1 != null. resource1 = ... // Obtain a resource object and assign it to variable resource2. This may throw an exception. // If successful, resource2 != null. Not reached if an exception has been thrown above. resource2 = ... // Perform operations on the resources. This may throw an exception. Not reached if an exception has been // thrown above. Note: Treat the variables resource1 and resource2 the same way as if they would have been // declared with the final modifier - that is - do NOT write anyting like resource1 = something else or // resource2 = something else here. resource1 ... resource2 ... // Finally, close the resources and set the variables to null indicating successful completion. // This may throw an exception. Not reached if an exception has been thrown above. resource1.close(); resource1 = null; // This may throw an exception. Not reached if an exception has been thrown above. resource2.close(); resource2 = null; // All resources are closed at this point and all operations (up to here) completed successfully without // throwing an exception we would need to handle (by letting it propagate or by catching and handling it). } finally { // Cleanup any resource not closed in the try block due to an exception having been thrown and suppress any // exception this may produce to not stop the exception from the try block to be propagated. If the try // block completed successfully, all variables will have been set to null there and this will not do // anything. This is just to cleanup properly in case of an exception. IOUtil.close( resource1 ); IOUtil.close( resource2 ); // Without that utility method you would need to write the following: // // try // { // if ( resource1 != null ) // { // resource1.close(); // } // } // catch( IOException e ) // { // Suppressed. If resource1 != null, an exception has already been thrown in the try block we need to // propagate instead of this one. // } // finally // { // try // { // if ( resource2 != null ) // { // resource2.close(); // } // } // catch ( IOException e ) // { // Suppressed. If resource2 != null, an exception has already been thrown in the try block we need to // propagate instead of this one. // } // } }
- Parameters:
inputStream
- The stream to close ornull
.
-
close
public static void close(@Nullable java.io.OutputStream outputStream)
Closes anOutputStream
suppressing anyIOException
.Note:
The usecase justifying this method is a shortcoming of the Java language up to but not including Java 7. For any code targeting Java 7 or later use of this method is highly discouraged and thetry-with-resources
statement should be used instead. Care must be taken to not use this method in a wayIOException
s get suppressed incorrectly. You must close all resources in use inside thetry
block to not suppress exceptions in thefinally
block incorrectly by using this method.Example:
// Introduce variables for the resources and initialize them to null. This cannot throw an exception. Closeable resource1 = null; Closeable resource2 = null; try { // Obtain a resource object and assign it to variable resource1. This may throw an exception. // If successful, resource1 != null. resource1 = ... // Obtain a resource object and assign it to variable resource2. This may throw an exception. // If successful, resource2 != null. Not reached if an exception has been thrown above. resource2 = ... // Perform operations on the resources. This may throw an exception. Not reached if an exception has been // thrown above. Note: Treat the variables resource1 and resource2 the same way as if they would have been // declared with the final modifier - that is - do NOT write anyting like resource1 = something else or // resource2 = something else here. resource1 ... resource2 ... // Finally, close the resources and set the variables to null indicating successful completion. // This may throw an exception. Not reached if an exception has been thrown above. resource1.close(); resource1 = null; // This may throw an exception. Not reached if an exception has been thrown above. resource2.close(); resource2 = null; // All resources are closed at this point and all operations (up to here) completed successfully without // throwing an exception we would need to handle (by letting it propagate or by catching and handling it). } finally { // Cleanup any resource not closed in the try block due to an exception having been thrown and suppress any // exception this may produce to not stop the exception from the try block to be propagated. If the try // block completed successfully, all variables will have been set to null there and this will not do // anything. This is just to cleanup properly in case of an exception. IOUtil.close( resource1 ); IOUtil.close( resource2 ); // Without that utility method you would need to write the following: // // try // { // if ( resource1 != null ) // { // resource1.close(); // } // } // catch( IOException e ) // { // Suppressed. If resource1 != null, an exception has already been thrown in the try block we need to // propagate instead of this one. // } // finally // { // try // { // if ( resource2 != null ) // { // resource2.close(); // } // } // catch ( IOException e ) // { // Suppressed. If resource2 != null, an exception has already been thrown in the try block we need to // propagate instead of this one. // } // } }
- Parameters:
outputStream
- The stream to close ornull
.
-
close
public static void close(@Nullable java.io.Reader reader)
Closes aReader
suppressing anyIOException
.Note:
The usecase justifying this method is a shortcoming of the Java language up to but not including Java 7. For any code targeting Java 7 or later use of this method is highly discouraged and thetry-with-resources
statement should be used instead. Care must be taken to not use this method in a wayIOException
s get suppressed incorrectly. You must close all resources in use inside thetry
block to not suppress exceptions in thefinally
block incorrectly by using this method.Example:
// Introduce variables for the resources and initialize them to null. This cannot throw an exception. Closeable resource1 = null; Closeable resource2 = null; try { // Obtain a resource object and assign it to variable resource1. This may throw an exception. // If successful, resource1 != null. resource1 = ... // Obtain a resource object and assign it to variable resource2. This may throw an exception. // If successful, resource2 != null. Not reached if an exception has been thrown above. resource2 = ... // Perform operations on the resources. This may throw an exception. Not reached if an exception has been // thrown above. Note: Treat the variables resource1 and resource2 the same way as if they would have been // declared with the final modifier - that is - do NOT write anyting like resource1 = something else or // resource2 = something else here. resource1 ... resource2 ... // Finally, close the resources and set the variables to null indicating successful completion. // This may throw an exception. Not reached if an exception has been thrown above. resource1.close(); resource1 = null; // This may throw an exception. Not reached if an exception has been thrown above. resource2.close(); resource2 = null; // All resources are closed at this point and all operations (up to here) completed successfully without // throwing an exception we would need to handle (by letting it propagate or by catching and handling it). } finally { // Cleanup any resource not closed in the try block due to an exception having been thrown and suppress any // exception this may produce to not stop the exception from the try block to be propagated. If the try // block completed successfully, all variables will have been set to null there and this will not do // anything. This is just to cleanup properly in case of an exception. IOUtil.close( resource1 ); IOUtil.close( resource2 ); // Without that utility method you would need to write the following: // // try // { // if ( resource1 != null ) // { // resource1.close(); // } // } // catch( IOException e ) // { // Suppressed. If resource1 != null, an exception has already been thrown in the try block we need to // propagate instead of this one. // } // finally // { // try // { // if ( resource2 != null ) // { // resource2.close(); // } // } // catch ( IOException e ) // { // Suppressed. If resource2 != null, an exception has already been thrown in the try block we need to // propagate instead of this one. // } // } }
- Parameters:
reader
- The reader to close ornull
.
-
close
public static void close(@Nullable java.io.Writer writer)
Closes aWriter
suppressing anyIOException
.Note:
The usecase justifying this method is a shortcoming of the Java language up to but not including Java 7. For any code targeting Java 7 or later use of this method is highly discouraged and thetry-with-resources
statement should be used instead. Care must be taken to not use this method in a wayIOException
s get suppressed incorrectly. You must close all resources in use inside thetry
block to not suppress exceptions in thefinally
block incorrectly by using this method.Example:
// Introduce variables for the resources and initialize them to null. This cannot throw an exception. Closeable resource1 = null; Closeable resource2 = null; try { // Obtain a resource object and assign it to variable resource1. This may throw an exception. // If successful, resource1 != null. resource1 = ... // Obtain a resource object and assign it to variable resource2. This may throw an exception. // If successful, resource2 != null. Not reached if an exception has been thrown above. resource2 = ... // Perform operations on the resources. This may throw an exception. Not reached if an exception has been // thrown above. Note: Treat the variables resource1 and resource2 the same way as if they would have been // declared with the final modifier - that is - do NOT write anyting like resource1 = something else or // resource2 = something else here. resource1 ... resource2 ... // Finally, close the resources and set the variables to null indicating successful completion. // This may throw an exception. Not reached if an exception has been thrown above. resource1.close(); resource1 = null; // This may throw an exception. Not reached if an exception has been thrown above. resource2.close(); resource2 = null; // All resources are closed at this point and all operations (up to here) completed successfully without // throwing an exception we would need to handle (by letting it propagate or by catching and handling it). } finally { // Cleanup any resource not closed in the try block due to an exception having been thrown and suppress any // exception this may produce to not stop the exception from the try block to be propagated. If the try // block completed successfully, all variables will have been set to null there and this will not do // anything. This is just to cleanup properly in case of an exception. IOUtil.close( resource1 ); IOUtil.close( resource2 ); // Without that utility method you would need to write the following: // // try // { // if ( resource1 != null ) // { // resource1.close(); // } // } // catch( IOException e ) // { // Suppressed. If resource1 != null, an exception has already been thrown in the try block we need to // propagate instead of this one. // } // finally // { // try // { // if ( resource2 != null ) // { // resource2.close(); // } // } // catch ( IOException e ) // { // Suppressed. If resource2 != null, an exception has already been thrown in the try block we need to // propagate instead of this one. // } // } }
- Parameters:
writer
- The writer to close ornull
.
-
-