Package org.apache.maven.shared.utils.io

Class IOUtil

java.lang.Object
org.apache.maven.shared.utils.io.IOUtil
public final class IOUtil extends Object

General IO Stream manipulation.

This class provides static utility methods for input/output operations, particularly buffered copying between sources (InputStream, Reader, String and byte[]) and destinations (OutputStream, Writer, String and byte[]).

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 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 the copy methods in Buffered* 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 further read requests can inexpensively get their data (until the buffer runs out).

However, the copy methods do the same thing, keeping an internal buffer, populated by InputStream.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 $Revision$ $Date$
Author:
Peter Donald, Jeff Turner

  • Method Summary

    Modifier and Type
    Method
    Description
    static void
    close(InputStream inputStream)
    Deprecated.
    use try-with-resources
    static void
    close(OutputStream outputStream)
    Deprecated.
    use try-with-resources
    static void
    close(Reader reader)
    Deprecated.
    use try-with-resources
    static void
    close(Writer writer)
    Deprecated.
    use try-with-resources
    static void
    close(Channel channel)
    Deprecated.
    use try-with-resources
    static boolean
    contentEquals(InputStream input1, InputStream input2)
    Deprecated.
    use org.apache.commons.io.IOUtils.contentEquals()
    static void
    copy(byte[] input, OutputStream output)
    Deprecated.
    inline this method
    static void
    copy(byte[] input, Writer output)
    Deprecated.
    always specify a character encoding
    static void
    copy(byte[] input, Writer output, int bufferSize)
    Deprecated.
    always specify a character encoding
    static void
    copy(byte[] input, Writer output, String encoding)
    Deprecated.
    use org.apache.commons.io.IOUtils.write().
    static void
    copy(byte[] input, Writer output, String encoding, int bufferSize)
    Deprecated.
    use org.apache.commons.io.IOUtils.write().
    static void
    copy(InputStream input, OutputStream output)
    Deprecated.
    use org.apache.commons.io.IOUtils.copy() or in Java 9 and later InputStream.transferTo().
    static void
    copy(InputStream input, OutputStream output, int bufferSize)
    Deprecated.
    use org.apache.commons.io.IOUtils.copy() or in Java 9 and later InputStream.transferTo().
    static void
    copy(InputStream input, Writer output)
    Deprecated.
    use org.apache.commons.io.IOUtils.copy().
    static void
    copy(InputStream input, Writer output, int bufferSize)
    Deprecated.
    use org.apache.commons.io.IOUtils.copy().
    static void
    copy(InputStream input, Writer output, String encoding)
    Deprecated.
    use org.apache.commons.io.IOUtils.copy().
    static void
    copy(InputStream input, Writer output, String encoding, int bufferSize)
    Deprecated.
    use org.apache.commons.io.IOUtils.copy().
    static void
    copy(Reader input, OutputStream output)
    Deprecated.
    always specify a character encoding
    static void
    copy(Reader input, OutputStream output, int bufferSize)
    Deprecated.
    always specify a character encoding
    static void
    copy(Reader input, Writer output)
    Deprecated.
    static void
    copy(Reader input, Writer output, int bufferSize)
    Deprecated.
    use org.apache.commons.io.IOUtils.copy().
    static void
    copy(String input, OutputStream output)
    Deprecated.
    always specify a character encoding
    static void
    copy(String input, OutputStream output, int bufferSize)
    Deprecated.
    always specify a character encoding
    static void
    copy(String input, Writer output)
    Deprecated.
    use org.apache.commons.io.IOUtils.write().
    static byte[]
    toByteArray(InputStream input)
    Deprecated.
    use org.apache.commons.io.IOUtils.readFully().
    static byte[]
    toByteArray(InputStream input, int bufferSize)
    Deprecated.
    use org.apache.commons.io.IOUtils.readFully().
    static byte[]
    toByteArray(Reader input)
    Deprecated.
    always specify a character encoding
    static byte[]
    toByteArray(Reader input, int bufferSize)
    Deprecated.
    always specify a character encoding
    static byte[]
    toByteArray(String input)
    Deprecated.
    always specify a character encoding
    static byte[]
    toByteArray(String input, int bufferSize)
    Deprecated.
    always specify a character encoding
    static String
    toString(byte[] input)
    Deprecated.
    always specify a character encoding
    static String
    toString(byte[] input, int bufferSize)
    Deprecated.
    always specify a character encoding
    static String
    toString(byte[] input, String encoding)
    Deprecated.
    use new String(input, encoding)
    static String
    toString(byte[] input, String encoding, int bufferSize)
    Deprecated.
    use new String(input, encoding)
    static String
    toString(InputStream input)
    Deprecated.
    always specify a character encoding
    static String
    toString(InputStream input, int bufferSize)
    Deprecated.
    always specify a character encoding
    static String
    toString(InputStream input, String encoding)
    Deprecated.
    use org.apache.commons.io.IOUtils.toString().
    static String
    toString(InputStream input, String encoding, int bufferSize)
    Deprecated.
    use org.apache.commons.io.IOUtils.toString().
    static String
    toString(Reader input)
    Deprecated.
    use org.apache.commons.io.IOUtils.toString().
    static String
    toString(Reader input, int bufferSize)
    Deprecated.
    use org.apache.commons.io.IOUtils.toString().

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Method Details

    • copy

      @Deprecated public static void copy(@Nonnull InputStream input, @Nonnull OutputStream output) throws IOException
      Deprecated.
      use org.apache.commons.io.IOUtils.copy() or in Java 9 and later InputStream.transferTo().
      Copy bytes from an InputStream to an OutputStream.
      Parameters:
      input - the stream to read from
      output - the stream to write to
      Throws:
      IOException - in case of an error

    • copy

      @Deprecated public static void copy(@Nonnull InputStream input, @Nonnull OutputStream output, int bufferSize) throws IOException
      Deprecated.
      use org.apache.commons.io.IOUtils.copy() or in Java 9 and later InputStream.transferTo().
      Copy bytes from an InputStream to an OutputStream. In Java 9 and later this is replaced by InputStream.transferTo().
      Parameters:
      input - the stream to read from
      output - the stream to write to
      bufferSize - size of internal buffer
      Throws:
      IOException - in case of an error

    • copy

      @Deprecated public static void copy(@Nonnull Reader input, @Nonnull Writer output) throws IOException
      Deprecated.
      Copy chars from a Reader to a Writer.
      Parameters:
      input - the reader to read from
      output - the writer to write to
      Throws:
      IOException - in case of failure * @deprecated use org.apache.commons.io.IOUtils.copy().

    • copy

      @Deprecated public static void copy(@Nonnull Reader input, @Nonnull Writer output, int bufferSize) throws IOException
      Deprecated.
      use org.apache.commons.io.IOUtils.copy().
      Copy chars from a Reader to a Writer.
      Parameters:
      input - the reader to read from
      output - the writer to write to
      bufferSize - size of internal buffer
      Throws:
      IOException - in case of failure

    • copy

      @Deprecated public static void copy(@Nonnull InputStream input, @Nonnull Writer output) throws IOException
      Deprecated.
      use org.apache.commons.io.IOUtils.copy().
      Copy and convert bytes from an InputStream to chars on a Writer. The platform's default encoding is used for the byte-to-char conversion.
      Parameters:
      input - the reader to read from
      output - the writer to write to
      Throws:
      IOException - in case of failure

    • copy

      @Deprecated public static void copy(@Nonnull InputStream input, @Nonnull Writer output, int bufferSize) throws IOException
      Deprecated.
      use org.apache.commons.io.IOUtils.copy().
      Copy and convert bytes from an InputStream to chars on a Writer. The platform's default encoding is used for the byte-to-char conversion.
      Parameters:
      input - the input stream to read from
      output - the writer to write to
      bufferSize - size of internal buffer
      Throws:
      IOException - in case of failure

    • copy

      @Deprecated public static void copy(@Nonnull InputStream input, @Nonnull Writer output, @Nonnull String encoding) throws IOException
      Deprecated.
      use org.apache.commons.io.IOUtils.copy().
      Copy and convert bytes from an InputStream to chars on a Writer, using the specified encoding.
      Parameters:
      input - the input stream to read from
      output - the writer to write to
      encoding - the name of a supported character encoding. See the IANA Charset Registry for a list of valid encoding types.
      Throws:
      IOException - in case of failure

    • copy

      @Deprecated public static void copy(@Nonnull InputStream input, @Nonnull Writer output, @Nonnull String encoding, int bufferSize) throws IOException
      Deprecated.
      use org.apache.commons.io.IOUtils.copy().
      Copy and convert bytes from an InputStream to chars on a Writer, 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 stream to read from
      output - the writer to write to
      bufferSize - size of internal buffer
      Throws:
      IOException - in case of failure

    • toString

      @Deprecated @Nonnull public static String toString(@Nonnull InputStream input) throws IOException
      Deprecated.
      always specify a character encoding
      Get the contents of an InputStream as a String. The platform's default encoding is used for the byte-to-char conversion.
      Parameters:
      input - the InputStream to read from
      Returns:
      the resulting string
      Throws:
      IOException - in case of failure

    • toString

      @Deprecated @Nonnull public static String toString(@Nonnull InputStream input, int bufferSize) throws IOException
      Deprecated.
      always specify a character encoding
      Get the contents of an InputStream as a String. The platform's default encoding is used for the byte-to-char conversion.
      Parameters:
      input - the InputStream to read from
      bufferSize - size of internal buffer
      Returns:
      the resulting string
      Throws:
      IOException - in case of failure

    • toString

      @Deprecated @Nonnull public static String toString(@Nonnull InputStream input, @Nonnull String encoding) throws IOException
      Deprecated.
      use org.apache.commons.io.IOUtils.toString().
      Get the contents of an InputStream as a String.
      Parameters:
      input - the InputStream to read from
      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:
      IOException - in case of failure

    • toString

      @Deprecated @Nonnull public static String toString(@Nonnull InputStream input, @Nonnull String encoding, int bufferSize) throws IOException
      Deprecated.
      use org.apache.commons.io.IOUtils.toString().
      Get the contents of an InputStream as a String.
      Parameters:
      input - the InputStream to read from
      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
      Returns:
      The converted string.
      Throws:
      IOException - in case of failure

    • toByteArray

      @Deprecated @Nonnull public static byte[] toByteArray(@Nonnull InputStream input) throws IOException
      Deprecated.
      use org.apache.commons.io.IOUtils.readFully().
      Get the contents of an InputStream as a byte[].
      Parameters:
      input - the InputStream to read from
      Returns:
      the resulting byte array.
      Throws:
      IOException - in case of failure

    • toByteArray

      @Deprecated @Nonnull public static byte[] toByteArray(@Nonnull InputStream input, int bufferSize) throws IOException
      Deprecated.
      use org.apache.commons.io.IOUtils.readFully().
      Get the contents of an InputStream as a byte[].
      Parameters:
      input - the InputStream to read from
      bufferSize - size of internal buffer
      Returns:
      the resulting byte array.
      Throws:
      IOException - in case of failure

    • copy

      @Deprecated public static void copy(@Nonnull Reader input, @Nonnull OutputStream output) throws IOException
      Deprecated.
      always specify a character encoding
      Serialize chars from a Reader to bytes on an OutputStream, and flush the OutputStream.
      Parameters:
      input - the InputStream to read from
      output - the output stream to write to
      Throws:
      IOException - in case of failure

    • copy

      @Deprecated public static void copy(@Nonnull Reader input, @Nonnull OutputStream output, int bufferSize) throws IOException
      Deprecated.
      always specify a character encoding
      Serialize chars from a Reader to bytes on an OutputStream, and flush the OutputStream.
      Parameters:
      input - the InputStream to read from
      output - the output to write to
      bufferSize - size of internal buffer
      Throws:
      IOException - in case of failure

    • toString

      @Deprecated @Nonnull public static String toString(@Nonnull Reader input) throws IOException
      Deprecated.
      use org.apache.commons.io.IOUtils.toString().
      Get the contents of a Reader as a String.
      Parameters:
      input - the InputStream to read from
      Returns:
      The converted string.
      Throws:
      IOException - in case of failure

    • toString

      @Deprecated @Nonnull public static String toString(@Nonnull Reader input, int bufferSize) throws IOException
      Deprecated.
      use org.apache.commons.io.IOUtils.toString().
      Get the contents of a Reader as a String.
      Parameters:
      input - the reader to read from
      bufferSize - size of internal buffer
      Returns:
      the resulting byte array.
      Throws:
      IOException - in case of failure

    • toByteArray

      @Deprecated @Nonnull public static byte[] toByteArray(@Nonnull Reader input) throws IOException
      Deprecated.
      always specify a character encoding
      Get the contents of a Reader as a byte[].
      Parameters:
      input - the InputStream to read from
      Returns:
      the resulting byte array.
      Throws:
      IOException - in case of failure

    • toByteArray

      @Deprecated @Nonnull public static byte[] toByteArray(@Nonnull Reader input, int bufferSize) throws IOException
      Deprecated.
      always specify a character encoding
      Get the contents of a Reader as a byte[].
      Parameters:
      input - the InputStream to read from
      bufferSize - size of internal buffer
      Returns:
      the resulting byte array.
      Throws:
      IOException - in case of failure

    • copy

      @Deprecated public static void copy(@Nonnull String input, @Nonnull OutputStream output) throws IOException
      Deprecated.
      always specify a character encoding
      Serialize chars from a String to bytes on an OutputStream, and flush the OutputStream.
      Parameters:
      input - the InputStream to read from
      output - the output to write to
      Throws:
      IOException - in case of failure

    • copy

      @Deprecated public static void copy(@Nonnull String input, @Nonnull OutputStream output, int bufferSize) throws IOException
      Deprecated.
      always specify a character encoding
      Serialize chars from a String to bytes on an OutputStream, and flush the OutputStream.
      Parameters:
      input - the InputStream to read from
      output - the output to write to
      bufferSize - size of internal buffer
      Throws:
      IOException - in case of failure

    • copy

      @Deprecated public static void copy(@Nonnull String input, @Nonnull Writer output) throws IOException
      Deprecated.
      use org.apache.commons.io.IOUtils.write().
      Copy chars from a String to a Writer.
      Parameters:
      input - the string to write
      output - resulting output Writer
      Throws:
      IOException - in case of failure

    • toByteArray

      @Deprecated @Nonnull public static byte[] toByteArray(@Nonnull String input) throws IOException
      Deprecated.
      always specify a character encoding
      Get the contents of a String as a byte[].
      Parameters:
      input - the String to read from
      Returns:
      the resulting byte array
      Throws:
      IOException - in case of failure

    • toByteArray

      @Deprecated @Nonnull public static byte[] toByteArray(@Nonnull String input, int bufferSize) throws IOException
      Deprecated.
      always specify a character encoding
      Get the contents of a String as a byte[].
      Parameters:
      input - the InputStream to read from
      bufferSize - size of internal buffer
      Returns:
      the resulting byte array
      Throws:
      IOException - in case of failure

    • copy

      @Deprecated public static void copy(@Nonnull byte[] input, @Nonnull Writer output) throws IOException
      Deprecated.
      always specify a character encoding
      Copy and convert bytes from a byte[] to chars on a Writer. The platform's default encoding is used for the byte-to-char conversion.
      Parameters:
      input - the InputStream to read from
      output - the output to write to
      Throws:
      IOException - in case of failure

    • copy

      @Deprecated public static void copy(@Nonnull byte[] input, @Nonnull Writer output, int bufferSize) throws IOException
      Deprecated.
      always specify a character encoding
      Copy and convert bytes from a byte[] to chars on a Writer. The platform's default encoding is used for the byte-to-char conversion.
      Parameters:
      input - the InputStream to read from
      output - the output to write to
      bufferSize - size of internal buffer
      Throws:
      IOException - in case of failure

    • copy

      @Deprecated public static void copy(@Nonnull byte[] input, @Nonnull Writer output, String encoding) throws IOException
      Deprecated.
      use org.apache.commons.io.IOUtils.write().
      Copy and convert bytes from a byte[] to chars on a Writer, 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 data to write
      output - the writer to write to
      Throws:
      IOException - in case of failure

    • copy

      @Deprecated public static void copy(@Nonnull byte[] input, @Nonnull Writer output, @Nonnull String encoding, int bufferSize) throws IOException
      Deprecated.
      use org.apache.commons.io.IOUtils.write().
      Copy and convert bytes from a byte[] to chars on a Writer, 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 buffer Writer
      bufferSize - size of internal buffer
      Throws:
      IOException - in case of failure

    • toString

      @Deprecated @Nonnull public static String toString(@Nonnull byte[] input) throws IOException
      Deprecated.
      always specify a character encoding
      Get the contents of a byte[] 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:
      IOException - in case of failure

    • toString

      @Deprecated @Nonnull public static String toString(@Nonnull byte[] input, int bufferSize) throws IOException
      Deprecated.
      always specify a character encoding
      Get the contents of a byte[] as a String. The platform's default encoding is used for the byte-to-char conversion.
      Parameters:
      bufferSize - size of internal buffer
      input - the input bytes
      Returns:
      the created string
      Throws:
      IOException - in case of failure

    • toString

      @Deprecated @Nonnull public static String toString(@Nonnull byte[] input, @Nonnull String encoding) throws IOException
      Deprecated.
      use new String(input, encoding)
      Get the contents of a byte[] 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:
      IOException - in case of failure

    • toString

      @Deprecated @Nonnull public static String toString(@Nonnull byte[] input, @Nonnull String encoding, int bufferSize) throws IOException
      Deprecated.
      use new String(input, encoding)
      Get the contents of a byte[] 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
      input - input bytes
      Returns:
      the resulting string
      Throws:
      IOException - in case of failure

    • copy

      @Deprecated public static void copy(@Nonnull byte[] input, @Nonnull OutputStream output) throws IOException
      Deprecated.
      inline this method
      Copy bytes from a byte[] to an OutputStream.
      Parameters:
      input - Input byte array.
      output - output stream OutputStream
      Throws:
      IOException - in case of failure

    • contentEquals

      @Deprecated public static boolean contentEquals(@Nonnull InputStream input1, @Nonnull InputStream input2) throws IOException
      Deprecated.
      use org.apache.commons.io.IOUtils.contentEquals()
      Compare the contents of two streams to determine if they are equal or not.
      Parameters:
      input1 - the first stream
      input2 - the second stream
      Returns:
      true if the content of the streams are equal or they both don't exist, false otherwise
      Throws:
      IOException - in case of failure

    • close

      @Deprecated public static void close(@Nullable Channel channel)
      Deprecated.
      use try-with-resources

      Closes a Channel suppressing any IOException.

      Note: The use case 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 the try-with-resources statement should be used instead. Care must be taken to not use this method in a way IOExceptions get suppressed incorrectly. You must close all resources in use inside the try block to not suppress exceptions in the finally 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 or null.

    • close

      @Deprecated public static void close(@Nullable InputStream inputStream)
      Deprecated.
      use try-with-resources

      Closes an InputStream suppressing any IOException.

      Note: The use case 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 the try-with-resources statement should be used instead. Care must be taken to not use this method in a way IOExceptions get suppressed incorrectly. You must close all resources in use inside the try block to not suppress exceptions in the finally 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 or null.

    • close

      @Deprecated public static void close(@Nullable OutputStream outputStream)
      Deprecated.
      use try-with-resources

      Closes an OutputStream suppressing any IOException.

      Note: The use case 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 the try-with-resources statement should be used instead. Care must be taken to not use this method in a way IOExceptions get suppressed incorrectly. You must close all resources in use inside the try block to not suppress exceptions in the finally 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 or null.

    • close

      @Deprecated public static void close(@Nullable Reader reader)
      Deprecated.
      use try-with-resources

      Closes a Reader suppressing any IOException.

      Note: The use case 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 the try-with-resources statement should be used instead. Care must be taken to not use this method in a way IOExceptions get suppressed incorrectly. You must close all resources in use inside the try block to not suppress exceptions in the finally 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 or null.

    • close

      @Deprecated public static void close(@Nullable Writer writer)
      Deprecated.
      use try-with-resources

      Closes a Writer suppressing any IOException.

      Note: The use case 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 the try-with-resources statement should be used instead. Care must be taken to not use this method in a way IOExceptions get suppressed incorrectly. You must close all resources in use inside the try block to not suppress exceptions in the finally 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 or null.