ioutils.java

j2me简单实例,j2me教程加源码,希望大家喜欢

/*
 * Copyright 2001-2006 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.io;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.CharArrayWriter;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.Reader;
import java.io.StringWriter;
import java.io.Writer;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;

import org.apache.commons.io.output.ByteArrayOutputStream;

/**
 * General IO stream manipulation utilities.
 * <p>
 * This class provides static utility methods for input/output operations.
 * <ul>
 * <li>closeQuietly - these methods close a stream ignoring nulls and exceptions
 * <li>toXxx/read - these methods read data from a stream
 * <li>write - these methods write data to a stream
 * <li>copy - these methods copy all the data from one stream to another
 * <li>contentEquals - these methods compare the content of two streams
 * </ul>
 * <p>
 * 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.
 * <p>
 * All the methods in this class that read a stream are buffered internally.
 * This means that there is no cause to use a <code>BufferedInputStream</code>
 * or <code>BufferedReader</code>. The default buffer size of 4K has been shown
 * to be efficient in tests.
 * <p>
 * Wherever possible, the methods in this class do <em>not</em> 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.
 * <p>
 * Origin of code: Excalibur.
 *
 * @author Peter Donald
 * @author Jeff Turner
 * @author Matthew Hawthorne
 * @author Stephen Colebourne
 * @author Gareth Davis
 * @author Ian Springer
 * @author Niall Pemberton
 * @author Sandy McArthur
 * @version $Id: IOUtils.java 385117 2006-03-11 18:07:02Z scolebourne $
 */
public class IOUtils {
    // NOTE: This class is focussed on InputStream, OutputStream, Reader and
    // Writer. Each method should take at least one of these as a parameter,
    // or return one of them.

    /**
     * The Unix directory separator character.
     */
    public static final char DIR_SEPARATOR_UNIX = '/';
    /**
     * The Windows directory separator character.
     */
    public static final char DIR_SEPARATOR_WINDOWS = '\\';
    /**
     * The system directory separator character.
     */
    public static final char DIR_SEPARATOR = File.separatorChar;
    /**
     * The Unix line separator string.
     */
    public static final String LINE_SEPARATOR_UNIX = "\n";
    /**
     * The Windows line separator string.
     */
    public static final String LINE_SEPARATOR_WINDOWS = "\r\n";
    /**
     * The system line separator string.
     */
    public static final String LINE_SEPARATOR;
    static {
        // avoid security issues
        StringWriter buf = new StringWriter(4);
        PrintWriter out = new PrintWriter(buf);
        out.println();
        LINE_SEPARATOR = buf.toString();
    }

    /**
     * The default buffer size to use.
     */
    private static final int DEFAULT_BUFFER_SIZE = 1024 * 4;

    /**
     * Instances should NOT be constructed in standard programming.
     */
    public IOUtils() {
        super();
    }

    //-----------------------------------------------------------------------
    /**
     * Unconditionally close an <code>Reader</code>.
     * <p>
     * Equivalent to {@link Reader#close()}, except any exceptions will be ignored.
     * This is typically used in finally blocks.
     *
     * @param input  the Reader to close, may be null or already closed
     */
    public static void closeQuietly(Reader input) {
        try {
            if (input != null) {
                input.close();
            }
        } catch (IOException ioe) {
            // ignore
        }
    }

    /**
     * Unconditionally close a <code>Writer</code>.
     * <p>
     * Equivalent to {@link Writer#close()}, except any exceptions will be ignored.
     * This is typically used in finally blocks.
     *
     * @param output  the Writer to close, may be null or already closed
     */
    public static void closeQuietly(Writer output) {
        try {
            if (output != null) {
                output.close();
            }
        } catch (IOException ioe) {
            // ignore
        }
    }

    /**
     * Unconditionally close an <code>InputStream</code>.
     * <p>
     * Equivalent to {@link InputStream#close()}, except any exceptions will be ignored.
     * This is typically used in finally blocks.
     *
     * @param input  the InputStream to close, may be null or already closed
     */
    public static void closeQuietly(InputStream input) {
        try {
            if (input != null) {
                input.close();
            }
        } catch (IOException ioe) {
            // ignore
        }
    }

    /**
     * Unconditionally close an <code>OutputStream</code>.
     * <p>
     * Equivalent to {@link OutputStream#close()}, except any exceptions will be ignored.
     * This is typically used in finally blocks.
     *
     * @param output  the OutputStream to close, may be null or already closed
     */
    public static void closeQuietly(OutputStream output) {
        try {
            if (output != null) {
                output.close();
            }
        } catch (IOException ioe) {
            // ignore
        }
    }

    // read toByteArray
    //-----------------------------------------------------------------------
    /**
     * Get the contents of an <code>InputStream</code> as a <code>byte[]</code>.
     * <p>
     * This method buffers the input internally, so there is no need to use a
     * <code>BufferedInputStream</code>.
     * 
     * @param input  the <code>InputStream</code> to read from
     * @return the requested byte array
     * @throws NullPointerException if the input is null
     * @throws IOException if an I/O error occurs
     */
    public static byte[] toByteArray(InputStream input) throws IOException {
        ByteArrayOutputStream output = new ByteArrayOutputStream();
        copy(input, output);
        return output.toByteArray();
    }

    /**
     * Get the contents of a <code>Reader</code> as a <code>byte[]</code>
     * using the default character encoding of the platform.
     * <p>
     * This method buffers the input internally, so there is no need to use a
     * <code>BufferedReader</code>.
     * 
     * @param input  the <code>Reader</code> to read from
     * @return the requested byte array
     * @throws NullPointerException if the input is null
     * @throws IOException if an I/O error occurs
     */
    public static byte[] toByteArray(Reader input) throws IOException {
        ByteArrayOutputStream output = new ByteArrayOutputStream();
        copy(input, output);
        return output.toByteArray();
    }

    /**
     * Get the contents of a <code>Reader</code> as a <code>byte[]</code>
     * using the specified character encoding.
     * <p>
     * Character encoding names can be found at
     * <a href="http://www.iana.org/assignments/character-sets">IANA</a>.
     * <p>
     * This method buffers the input internally, so there is no need to use a
     * <code>BufferedReader</code>.
     * 
     * @param input  the <code>Reader</code> to read from
     * @param encoding  the encoding to use, null means platform default
     * @return the requested byte array
     * @throws NullPointerException if the input is null
     * @throws IOException if an I/O error occurs
     * @since Commons IO 1.1
     */
    public static byte[] toByteArray(Reader input, String encoding)
            throws IOException {
        ByteArrayOutputStream output = new ByteArrayOutputStream();
        copy(input, output, encoding);
        return output.toByteArray();
    }

    /**
     * Get the contents of a <code>String</code> as a <code>byte[]</code>
     * using the default character encoding of the platform.
     * <p>
     * This is the same as {@link String#getBytes()}.
     * 
     * @param input  the <code>String</code> to convert
     * @return the requested byte array
     * @throws NullPointerException if the input is null
     * @throws IOException if an I/O error occurs (never occurs)
     * @deprecated Use {@link String#getBytes()}
     */
    public static byte[] toByteArray(String input) throws IOException {
        return input.getBytes();
    }

    // read char[]
    //-----------------------------------------------------------------------
    /**
     * Get the contents of an <code>InputStream</code> as a character array
     * using the default character encoding of the platform.
     * <p>
     * This method buffers the input internally, so there is no need to use a
     * <code>BufferedInputStream</code>.
     * 
     * @param is  the <code>InputStream</code> to read from
     * @return the requested character array
     * @throws NullPointerException if the input is null
     * @throws IOException if an I/O error occurs
     * @since Commons IO 1.1
     */
    public static char[] toCharArray(InputStream is) throws IOException {
        CharArrayWriter output = new CharArrayWriter();
        copy(is, output);
        return output.toCharArray();
    }

    /**
     * Get the contents of an <code>InputStream</code> as a character array
     * using the specified character encoding.
     * <p>
     * Character encoding names can be found at
     * <a href="http://www.iana.org/assignments/character-sets">IANA</a>.