Java/File Input Output/StringReader

Read InputStream to string

  
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/** Utility class for working with streams.
 */
public final class Streams {
  /**
   * This convenience method allows to read a
   * {@link org.apache.rumons.fileupload.FileItemStream}"s
   * content into a string. The platform"s default character encoding
   * is used for converting bytes into characters.
   * @param pStream The input stream to read.
   * @see #asString(InputStream, String)
   * @return The streams contents, as a string.
   * @throws IOException An I/O error occurred.
   */
  public static String asString(InputStream pStream) throws IOException {
      ByteArrayOutputStream baos = new ByteArrayOutputStream();
      copy(pStream, baos, true);
      return baos.toString();
  }
  /**
   * This convenience method allows to read a
   * {@link org.apache.rumons.fileupload.FileItemStream}"s
   * content into a string, using the given character encoding.
   * @param pStream The input stream to read.
   * @param pEncoding The character encoding, typically "UTF-8".
   * @see #asString(InputStream)
   * @return The streams contents, as a string.
   * @throws IOException An I/O error occurred.
   */
  public static String asString(InputStream pStream, String pEncoding)
          throws IOException {
      ByteArrayOutputStream baos = new ByteArrayOutputStream();
      copy(pStream, baos, true);
      return baos.toString(pEncoding);
  }
    /**
     * Default buffer size for use in
     * {@link #copy(InputStream, OutputStream, boolean)}.
     */
    private static final int DEFAULT_BUFFER_SIZE = 8192;
    /**
     * Copies the contents of the given {@link InputStream}
     * to the given {@link OutputStream}. Shortcut for
     * <pre>
     *   copy(pInputStream, pOutputStream, new byte[8192]);
     * </pre>
     * @param pInputStream The input stream, which is being read.
     * It is guaranteed, that {@link InputStream#close()} is called
     * on the stream.
     * @param pOutputStream The output stream, to which data should
     * be written. May be null, in which case the input streams
     * contents are simply discarded.
     * @param pClose True guarantees, that {@link OutputStream#close()}
     * is called on the stream. False indicates, that only
     * {@link OutputStream#flush()} should be called finally.
     *
     * @return Number of bytes, which have been copied.
     * @throws IOException An I/O error occurred.
     */
    public static long copy(InputStream pInputStream,
            OutputStream pOutputStream, boolean pClose)
            throws IOException {
        return copy(pInputStream, pOutputStream, pClose,
                new byte[DEFAULT_BUFFER_SIZE]);
    }
    /**
     * Copies the contents of the given {@link InputStream}
     * to the given {@link OutputStream}.
     * @param pIn The input stream, which is being read.
     *   It is guaranteed, that {@link InputStream#close()} is called
     *   on the stream.
     * @param pOut The output stream, to which data should
     *   be written. May be null, in which case the input streams
     *   contents are simply discarded.
     * @param pClose True guarantees, that {@link OutputStream#close()}
     *   is called on the stream. False indicates, that only
     *   {@link OutputStream#flush()} should be called finally.
     * @param pBuffer Temporary buffer, which is to be used for
     *   copying data.
     * @return Number of bytes, which have been copied.
     * @throws IOException An I/O error occurred.
     */
    public static long copy(InputStream pIn,
            OutputStream pOut, boolean pClose,
            byte[] pBuffer)
    throws IOException {
        OutputStream out = pOut;
        InputStream in = pIn;
        try {
            long total = 0;
            for (;;) {
                int res = in.read(pBuffer);
                if (res == -1) {
                    break;
                }
                if (res > 0) {
                    total += res;
                    if (out != null) {
                        out.write(pBuffer, 0, res);
                    }
                }
            }
            if (out != null) {
                if (pClose) {
                    out.close();
                } else {
                    out.flush();
                }
                out = null;
            }
            in.close();
            in = null;
            return total;
        } finally {
            if (in != null) {
                try {
                    in.close();
                } catch (Throwable t) {
                    /* Ignore me */
                }
            }
            if (pClose  &&  out != null) {
                try {
                    out.close();
                } catch (Throwable t) {
                    /* Ignore me */
                }
            }
        }
    }
}

Reads data off a stream, printing every byte read to System.err

  
/****************************************************************
 * Licensed to the Apache Software Foundation (ASF) under one   *
 * or more contributor license agreements.  See the NOTICE file *
 * distributed with this work for additional information        *
 * regarding copyright ownership.  The ASF licenses this file   *
 * to you 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.                                           *
 ****************************************************************/

import java.io.IOException;
import java.io.InputStream;
/**
 * Reads data off a stream, printing every byte read to System.err.
 */
public class DebugInputStream extends InputStream {
    /**
     * The input stream being wrapped
     */
    InputStream in = null;
    /**
     * Constructor that takes an InputStream to be wrapped.
     *
     * @param in the InputStream to be wrapped
     */
    public DebugInputStream(InputStream in) {
        this.in = in;
    }
    /**
     * Read a byte off the stream
     *
     * @return the byte read off the stream
     * @throws IOException if an exception is encountered when reading
     */
    public int read() throws IOException {
        int b = in.read();
        System.err.write(b);
        return b;
    }
    /**
     * Close the stream
     *
     * @throws IOException if an exception is encountered when closing
     */
    public void close() throws IOException {
        in.close();
    }
}

Reads file contents

  
/** 
 * 
 * The ObjectStyle Group Software License, version 1.1
 * ObjectStyle Group - http://objectstyle.org/
 * 
 * Copyright (c) 2002-2005, Andrei (Andrus) Adamchik and individual authors
 * of the software. All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 
 * 3. The end-user documentation included with the redistribution, if any,
 *    must include the following acknowlegement:
 *    "This product includes software developed by independent contributors
 *    and hosted on ObjectStyle Group web site (http://objectstyle.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 * 
 * 4. The names "ObjectStyle Group" and "Cayenne" must not be used to endorse
 *    or promote products derived from this software without prior written
 *    permission. For written permission, email
 *    "andrus at objectstyle dot org".
 * 
 * 5. Products derived from this software may not be called "ObjectStyle"
 *    or "Cayenne", nor may "ObjectStyle" or "Cayenne" appear in their
 *    names without prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED ``AS IS"" AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE OBJECTSTYLE GROUP OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * 
 * 
 * This software consists of voluntary contributions made by many
 * individuals and hosted on ObjectStyle Group web site.  For more
 * information on the ObjectStyle Group, please see
 * <http://objectstyle.org/>.
 */
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.io.Serializable;
import java.lang.reflect.Member;
import java.lang.reflect.Modifier;
import java.net.URL;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.ruparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.regex.Pattern;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
/**
 * Contains various unorganized static utility methods used across Cayenne.
 * 
 * @author Andrei Adamchik
 */
public class Util {
    /**
     * Reads file contents, returning it as a String, using System default line separator.
     */
    public static String stringFromFile(File file) throws IOException {
        return stringFromFile(file, System.getProperty("line.separator"));
    }
    /**
     * Reads file contents, returning it as a String, joining lines with provided
     * separator.
     */
    public static String stringFromFile(File file, String joinWith) throws IOException {
        StringBuffer buf = new StringBuffer();
        BufferedReader in = new BufferedReader(new FileReader(file));
        try {
            String line = null;
            while ((line = in.readLine()) != null) {
                buf.append(line).append(joinWith);
            }
        }
        finally {
            in.close();
        }
        return buf.toString();
    }
}

Reads from an underlying InputStream up to a defined number of bytes or the end of the underlying stream

  
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */
/* $Id: SubInputStream.java 604883 2007-12-17 14:36:37Z jeremias $ */

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
/**
 * This class is a FilterInputStream descendant that reads from an underlying InputStream
 * up to a defined number of bytes or the end of the underlying stream. Closing this InputStream
 * will not result in the underlying InputStream to be closed, too.
 * <p>
 * This InputStream can be used to read chunks from a larger file of which the length is
 * known in advance.
 */
public class SubInputStream extends FilterInputStream {
    /** Indicates the number of bytes remaining to be read from the underlying InputStream. */
    private long bytesToRead;
    
    /**
     * Indicates whether the underlying stream should be closed when the {@link #close()} method
     * is called.
     */ 
    private boolean closeUnderlying = false;
    
    /**
     * Creates a new SubInputStream.
     * @param in the InputStream to read from
     * @param maxLen the maximum number of bytes to read from the underlying InputStream until
     *               the end-of-file is signalled.
     * @param closeUnderlying true if the underlying stream should be closed when the
     *               {@link #close()} method is called.
     */
    public SubInputStream(InputStream in, long maxLen, boolean closeUnderlying) {
        super(in);
        this.bytesToRead = maxLen;
        this.closeUnderlying = closeUnderlying;
    }
    /**
     * Creates a new SubInputStream. The underlying stream is not closed, when close() is called.
     * @param in the InputStream to read from
     * @param maxLen the maximum number of bytes to read from the underlying InputStream until
     *               the end-of-file is signalled.
     */
    public SubInputStream(InputStream in, long maxLen) {
        this(in, maxLen, false);
    }
    /** {@inheritDoc} */
    public int read() throws IOException {
        if (bytesToRead > 0) {
            int result = super.read();
            if (result >= 0) {
                bytesToRead--;
                return result;
            } else {
                return -1;
            }
        } else {
            return -1;
        }
    }
    
    /** {@inheritDoc} */
    public int read(byte[] b, int off, int len) throws IOException {
        if (bytesToRead == 0) {
            return -1;
        }
        int effRead = (int)Math.min(bytesToRead, len);
        //cast to int is safe because len can never be bigger than Integer.MAX_VALUE
        
        int result = super.read(b, off, effRead);
        if (result >= 0) {
            bytesToRead -= result;
        }
        return result;
    }
    
    /** {@inheritDoc} */
    public long skip(long n) throws IOException {
        long effRead = Math.min(bytesToRead, n);
        long result = super.skip(effRead);
        bytesToRead -= result;
        return result;
    }
    /** {@inheritDoc} */
    public void close() throws IOException {
        this.bytesToRead = 0;
        if (this.closeUnderlying) {
            super.close();
        }
    }
}
//////////////////////////////////
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */
/* $Id: SubInputStreamTestCase.java 604883 2007-12-17 14:36:37Z jeremias $ */
 
package org.apache.xmlgraphics.util.io;
import java.io.ByteArrayInputStream;
import java.util.Arrays;
import junit.framework.TestCase;
/**
 * Test case for SubInputStream.
 */
public class SubInputStreamTestCase extends TestCase {
    /**
     * Main constructor.
     * @param name the test case"s name
     * @see junit.framework.TestCase#TestCase(String)
     */
    public SubInputStreamTestCase(String name) {
        super(name);
    }
    /**
     * Tests SubInputStream.
     * @throws Exception if an error occurs
     */
    public void testMain() throws Exception {
        //Initialize test data
        byte[] data = new byte[256];
        for (int i = 0; i < data.length; i++) {
            data[i] = (byte)(i & 0xff);
        }
        
        int v, c;
        byte[] buf;
        String s;
        
        SubInputStream subin = new SubInputStream(new ByteArrayInputStream(data), 10);
        v = subin.read();
        assertEquals(0, v);
        v = subin.read();
        assertEquals(1, v);
        
        buf = new byte[4];
        c = subin.read(buf);
        assertEquals(4, c);
        s = new String(buf, "US-ASCII");
        assertEquals("\u0002\u0003\u0004\u0005", s);
        
        Arrays.fill(buf, (byte)0);
        c = subin.read(buf, 2, 2);
        assertEquals(2, c);
        s = new String(buf, "US-ASCII");
        assertEquals("\u0000\u0000\u0006\u0007", s);
        
        Arrays.fill(buf, (byte)0);
        c = subin.read(buf);
        assertEquals(2, c);
        s = new String(buf, "US-ASCII");
        assertEquals("\u0008\u0009\u0000\u0000", s);
    }
    
}

Read string from InputStream and Reader

  
/*
 * $RCSfile: StringIO.java,v $
 *
 * Copyright (c) 2007 Sun Microsystems, Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistribution of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistribution in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in
 *   the documentation and/or other materials provided with the
 *   distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of
 * contributors may be used to endorse or promote products derived
 * from this software without specific prior written permission.
 *
 * This software is provided "AS IS," without a warranty of any
 * kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND
 * WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY
 * EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN") AND ITS LICENSORS SHALL
 * NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF
 * USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR
 * ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL,
 * CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND
 * REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF THE USE OF OR
 * INABILITY TO USE THIS SOFTWARE, EVEN IF SUN HAS BEEN ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGES.
 *
 * You acknowledge that this software is not designed, licensed or
 * intended for use in the design, construction, operation or
 * maintenance of any nuclear facility.
 *
 * $Revision: 1.4 $
 * $Date: 2007/02/09 17:20:42 $
 * $State: Exp $
 */
import java.io.IOException;
import java.io.File;
import java.io.FileReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.URL;
/**
 * Utility class with static methods to read the entire contents of a
 * file, URL, InputStream, or Reader into a single String that is
 * returned to the user.
 *
 * @since Java 3D 1.4
 */
public class StringIO {
    /**
     * Read the entire contents of the specified file and return a
     * single String object containing the contents of the file.
     *
     * @param fileName the name of the file from which to read
     *
     * @return a String containing the contents of the input file
     *
     * @throws IOException if the specified file cannot be opened, or
     * if an I/O error occurs while reading the file
     */
    public static String readFully(String fileName) throws IOException {
  return readFully(new File(fileName));
    }
    /**
     * Read the entire contents of the specified file and return a
     * single String object containing the contents of the file.
     * This method does not return until the end of the input file
     * is reached.
     *
     * @param file a File from which to read
     *
     * @return a String containing the contents of the input file
     *
     * @throws IOException if the specified file cannot be opened, or
     * if an I/O error occurs while reading the file
     */
    public static String readFully(File file) throws IOException {
  return readFully(new FileReader(file));
    }
    /**
     * Read the entire contents of the specified URL and return a
     * single String object containing the contents of the URL.
     * This method does not return until an end of stream is reached
     * for the URL.
     *
     * @param url a URL from which to read
     *
     * @return a String containing the contents of the input URL
     *
     * @throws IOException if the specified URL cannot be opened, or
     * if an I/O error occurs while reading the URL
     */
    public static String readFully(URL url) throws IOException {
  return readFully(url.openStream());
    }
    /**
     * Read the entire contents of the specified InputStream and return a
     * single String object containing the contents of the InputStream.
     * This method does not return until the end of the input
     * stream is reached.
     *
     * @param stream an InputStream from which to read
     *
     * @return a String containing the contents of the input stream
     *
     * @throws IOException if an I/O error occurs while reading the input stream
     */
    public static String readFully(InputStream stream) throws IOException {
  return readFully(new InputStreamReader(stream));
    }
    /**
     * Read the entire contents of the specified Reader and return a
     * single String object containing the contents of the InputStream.
     * This method does not return until the end of the input file or
     * stream is reached.
     *
     * @param reader a Reader from which to read
     *
     * @return a String containing the contents of the stream
     *
     * @throws IOException if an I/O error occurs while reading the input stream
     */
    public static String readFully(Reader reader) throws IOException {
  char[] arr = new char[8*1024]; // 8K at a time
  StringBuffer buf = new StringBuffer();
  int numChars;
  while ((numChars = reader.read(arr, 0, arr.length)) > 0) {
      buf.append(arr, 0, numChars);
  }
  return buf.toString();
    }

    /**
     * Do not construct an instance of this class.
     */
    private StringIO() {
    }
}

Using the StringReader class

  
import java.io.StreamTokenizer;
import java.io.StringReader;
public class Main {
  public static void main(String[] args) throws Exception{
    StringReader reader = new StringReader("this is a test");
    int wordCount = 0;
    StreamTokenizer streamTokenizer = new StreamTokenizer(reader);
    while (streamTokenizer.nextToken() != StreamTokenizer.TT_EOF) {
      if (streamTokenizer.ttype == StreamTokenizer.TT_WORD)
        wordCount++;
    }
    System.out.println("Number of words in file: " + wordCount);
  }
}
//Number of words in file: 4