Class IOUtils

java.lang.Object
org.zeroturnaround.zip.commons.IOUtils
public class IOUtils extends 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 $

  • Field Details

  • Constructor Details

    • IOUtils

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

  • Method Details

    • closeQuietly

      public static void closeQuietly(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(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(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(InputStream input) throws 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:
      NullPointerException - if the input is null
      IOException - if an I/O error occurs

    • toString

      public static String toString(InputStream input, String encoding) throws 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:
      NullPointerException - if the input is null
      IOException - if an I/O error occurs

    • copy

      public static int copy(InputStream input, OutputStream output) throws 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:
      NullPointerException - if the input or output is null
      IOException - if an I/O error occurs
      Since:
      1.1

    • copyLarge

      public static long copyLarge(InputStream input, OutputStream output) throws 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:
      NullPointerException - if the input or output is null
      IOException - if an I/O error occurs
      Since:
      1.3

    • copyLarge

      public static long copyLarge(InputStream input, OutputStream output, byte[] buffer) throws 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:
      NullPointerException - if the input or output is null
      IOException - if an I/O error occurs
      Since:
      2.2

    • copy

      public static void copy(InputStream input, Writer output) throws 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:
      NullPointerException - if the input or output is null
      IOException - if an I/O error occurs
      Since:
      1.1

    • copy

      public static void copy(InputStream input, Writer output, String encoding) throws 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:
      NullPointerException - if the input or output is null
      IOException - if an I/O error occurs
      Since:
      1.1

    • copy

      public static int copy(Reader input, Writer output) throws 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:
      NullPointerException - if the input or output is null
      IOException - if an I/O error occurs
      Since:
      1.1

    • copyLarge

      public static long copyLarge(Reader input, Writer output) throws 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:
      NullPointerException - if the input or output is null
      IOException - if an I/O error occurs
      Since:
      1.3

    • copyLarge

      public static long copyLarge(Reader input, Writer output, char[] buffer) throws 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:
      NullPointerException - if the input or output is null
      IOException - if an I/O error occurs
      Since:
      2.2

    • contentEquals

      public static boolean contentEquals(InputStream input1, InputStream input2) throws 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:
      NullPointerException - if either input is null
      IOException - if an I/O error occurs