Class IOUtils


  • public class IOUtils
    extends java.lang.Object
    This is a class that has been made significantly smaller (deleted a bunch of methods) and originally is from the Apache Commons IO 2.2 package (the latest version that supports Java 1.5). All license and other documentation is intact. General IO stream manipulation utilities.

    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.

    Version:
    $Id: IOUtils.java 1304177 2012-03-23 03:36:44Z ggregory $
    • Constructor Summary

      Constructors 
      Constructor Description
      IOUtils()
      Instances should NOT be constructed in standard programming.
    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static void closeQuietly​(java.io.Closeable closeable)
      Unconditionally close a Closeable.
      static void closeQuietly​(java.io.InputStream input)
      Unconditionally close an InputStream.
      static void closeQuietly​(java.io.OutputStream output)
      Unconditionally close an OutputStream.
      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 int copy​(java.io.InputStream input, java.io.OutputStream output)
      Copy bytes from an InputStream to an OutputStream.
      static void copy​(java.io.InputStream input, java.io.Writer output)
      Copy bytes from an InputStream to chars on a Writer using the default character encoding of the platform.
      static void copy​(java.io.InputStream input, java.io.Writer output, java.lang.String encoding)
      Copy bytes from an InputStream to chars on a Writer using the specified character encoding.
      static int copy​(java.io.Reader input, java.io.Writer output)
      Copy chars from a Reader to a Writer.
      static long copyLarge​(java.io.InputStream input, java.io.OutputStream output)
      Copy bytes from a large (over 2GB) InputStream to an OutputStream.
      static long copyLarge​(java.io.InputStream input, java.io.OutputStream output, byte[] buffer)
      Copy bytes from a large (over 2GB) InputStream to an OutputStream.
      static long copyLarge​(java.io.Reader input, java.io.Writer output)
      Copy chars from a large (over 2GB) Reader to a Writer.
      static long copyLarge​(java.io.Reader input, java.io.Writer output, char[] buffer)
      Copy chars from a large (over 2GB) Reader to a Writer.
      static byte[] toByteArray​(java.io.InputStream input)
      Get the contents of an InputStream as a byte[].
      static java.lang.String toString​(java.io.InputStream input, java.lang.String encoding)
      Get the contents of an InputStream as a String using the specified character encoding.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Field Detail

      • DIR_SEPARATOR_UNIX

        public static final char DIR_SEPARATOR_UNIX
        The Unix directory separator character.
        See Also:
        Constant Field Values
      • DIR_SEPARATOR_WINDOWS

        public static final char DIR_SEPARATOR_WINDOWS
        The Windows directory separator character.
        See Also:
        Constant Field Values
      • DIR_SEPARATOR

        public static final char DIR_SEPARATOR
        The system directory separator character.
      • LINE_SEPARATOR_UNIX

        public static final java.lang.String LINE_SEPARATOR_UNIX
        The Unix line separator string.
        See Also:
        Constant Field Values
      • LINE_SEPARATOR_WINDOWS

        public static final java.lang.String LINE_SEPARATOR_WINDOWS
        The Windows line separator string.
        See Also:
        Constant Field Values
      • LINE_SEPARATOR

        public static final java.lang.String LINE_SEPARATOR
        The system line separator string.
    • Constructor Detail

      • IOUtils

        public IOUtils()
        Instances should NOT be constructed in standard programming.
    • Method Detail

      • closeQuietly

        public static void closeQuietly​(java.io.InputStream input)
        Unconditionally close an InputStream.

        Equivalent to InputStream.close(), except any exceptions will be ignored. This is typically used in finally blocks.

        Example code:

           byte[] data = new byte[1024];
           InputStream in = null;
           try {
               in = new FileInputStream("foo.txt");
               in.read(data);
               in.close(); //close errors are handled
           } catch (Exception e) {
               // error handling
           } finally {
               IOUtils.closeQuietly(in);
           }
         
        Parameters:
        input - the InputStream to close, may be null or already closed
      • closeQuietly

        public static void closeQuietly​(java.io.OutputStream output)
        Unconditionally close an OutputStream.

        Equivalent to OutputStream.close(), except any exceptions will be ignored. This is typically used in finally blocks.

        Example code:

         byte[] data = "Hello, World".getBytes();
        
         OutputStream out = null;
         try {
             out = new FileOutputStream("foo.txt");
             out.write(data);
             out.close(); //close errors are handled
         } catch (IOException e) {
             // error handling
         } finally {
             IOUtils.closeQuietly(out);
         }
         
        Parameters:
        output - the OutputStream to close, may be null or already closed
      • closeQuietly

        public static void closeQuietly​(java.io.Closeable closeable)
        Unconditionally close a Closeable.

        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);
           }
         
        Parameters:
        closeable - the object to close, may be null or already closed
        Since:
        2.0
      • toByteArray

        public static byte[] toByteArray​(java.io.InputStream input)
                                  throws java.io.IOException
        Get the contents of an InputStream as a byte[].

        This method buffers the input internally, so there is no need to use a BufferedInputStream.

        Parameters:
        input - the InputStream to read from
        Returns:
        the requested byte array
        Throws:
        java.lang.NullPointerException - if the input is null
        java.io.IOException - if an I/O error occurs
      • toString

        public static java.lang.String toString​(java.io.InputStream input,
                                                java.lang.String encoding)
                                         throws java.io.IOException
        Get the contents of an InputStream as a String using the specified character encoding.

        Character encoding names can be found at IANA.

        This method buffers the input internally, so there is no need to use a BufferedInputStream.

        Parameters:
        input - the InputStream to read from
        encoding - the encoding to use, null means platform default
        Returns:
        the requested String
        Throws:
        java.lang.NullPointerException - if the input is null
        java.io.IOException - if an I/O error occurs
      • copy

        public static int copy​(java.io.InputStream input,
                               java.io.OutputStream output)
                        throws java.io.IOException
        Copy bytes from an 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.

        Parameters:
        input - the InputStream to read from
        output - the OutputStream to write to
        Returns:
        the number of bytes copied, or -1 if > Integer.MAX_VALUE
        Throws:
        java.lang.NullPointerException - if the input or output is null
        java.io.IOException - if an I/O error occurs
        Since:
        1.1
      • copyLarge

        public static long copyLarge​(java.io.InputStream input,
                                     java.io.OutputStream output)
                              throws java.io.IOException
        Copy bytes from a large (over 2GB) 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.

        Parameters:
        input - the InputStream to read from
        output - the OutputStream to write to
        Returns:
        the number of bytes copied
        Throws:
        java.lang.NullPointerException - if the input or output is null
        java.io.IOException - if an I/O error occurs
        Since:
        1.3
      • copyLarge

        public static long copyLarge​(java.io.InputStream input,
                                     java.io.OutputStream output,
                                     byte[] buffer)
                              throws java.io.IOException
        Copy bytes from a large (over 2GB) InputStream to an OutputStream.

        This method uses the provided buffer, so there is no need to use a BufferedInputStream.

        Parameters:
        input - the InputStream to read from
        output - the OutputStream to write to
        buffer - the buffer to use for the copy
        Returns:
        the number of bytes copied
        Throws:
        java.lang.NullPointerException - if the input or output is null
        java.io.IOException - if an I/O error occurs
        Since:
        2.2
      • copy

        public static void copy​(java.io.InputStream input,
                                java.io.Writer output)
                         throws java.io.IOException
        Copy bytes from an InputStream to chars on a Writer using the default character encoding of the platform.

        This method buffers the input internally, so there is no need to use a BufferedInputStream.

        This method uses InputStreamReader.

        Parameters:
        input - the InputStream to read from
        output - the Writer to write to
        Throws:
        java.lang.NullPointerException - if the input or output is null
        java.io.IOException - if an I/O error occurs
        Since:
        1.1
      • copy

        public static void copy​(java.io.InputStream input,
                                java.io.Writer output,
                                java.lang.String encoding)
                         throws java.io.IOException
        Copy bytes from an InputStream to chars on a Writer using the specified character encoding.

        This method buffers the input internally, so there is no need to use a BufferedInputStream.

        Character encoding names can be found at IANA.

        This method uses InputStreamReader.

        Parameters:
        input - the InputStream to read from
        output - the Writer to write to
        encoding - the encoding to use, null means platform default
        Throws:
        java.lang.NullPointerException - if the input or output is null
        java.io.IOException - if an I/O error occurs
        Since:
        1.1
      • copy

        public static int copy​(java.io.Reader input,
                               java.io.Writer output)
                        throws java.io.IOException
        Copy chars from a Reader to a Writer.

        This method buffers the input internally, so there is no need to use a BufferedReader.

        Large streams (over 2GB) will return a chars copied value of -1 after the copy has completed since the correct number of chars cannot be returned as an int. For large streams use the copyLarge(Reader, Writer) method.

        Parameters:
        input - the Reader to read from
        output - the Writer to write to
        Returns:
        the number of characters copied, or -1 if > Integer.MAX_VALUE
        Throws:
        java.lang.NullPointerException - if the input or output is null
        java.io.IOException - if an I/O error occurs
        Since:
        1.1
      • copyLarge

        public static long copyLarge​(java.io.Reader input,
                                     java.io.Writer output)
                              throws java.io.IOException
        Copy chars from a large (over 2GB) Reader to a Writer.

        This method buffers the input internally, so there is no need to use a BufferedReader.

        The buffer size is given by DEFAULT_BUFFER_SIZE.

        Parameters:
        input - the Reader to read from
        output - the Writer to write to
        Returns:
        the number of characters copied
        Throws:
        java.lang.NullPointerException - if the input or output is null
        java.io.IOException - if an I/O error occurs
        Since:
        1.3
      • copyLarge

        public static long copyLarge​(java.io.Reader input,
                                     java.io.Writer output,
                                     char[] buffer)
                              throws java.io.IOException
        Copy chars from a large (over 2GB) Reader to a Writer.

        This method uses the provided buffer, so there is no need to use a BufferedReader.

        Parameters:
        input - the Reader to read from
        output - the Writer to write to
        buffer - the buffer to be used for the copy
        Returns:
        the number of characters copied
        Throws:
        java.lang.NullPointerException - if the input or output is null
        java.io.IOException - if an I/O error occurs
        Since:
        2.2
      • contentEquals

        public static boolean contentEquals​(java.io.InputStream input1,
                                            java.io.InputStream input2)
                                     throws java.io.IOException
        Compare the contents of two Streams to determine if they are equal or not.

        This method buffers the input internally using BufferedInputStream if they are not already buffered.

        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:
        java.lang.NullPointerException - if either input is null
        java.io.IOException - if an I/O error occurs