programming-examples/java/Servlets_Session_Swing_Util/A utility class for reading and writing character.java

A utility class for reading and writing character files

package com.ack.util;

import java.io.*;

/**
 *  a utility class for reading and writing character
 *  files to and from to disk.  If you want to deal
 *  exclusively in bytes, use the ByteLoader class
 *  in this package.
 *
 *  Note that all methods in the FileUtil will read/write
 *  entire contents of all supplied Readers and Writers
 *  and alway close them before returning.
 *
 *  @see com.ack.util.ByteLoader
 */

public class FileUtil {
  private static final int kFILEBUFSIZE = 128;
  private static FileUtil fSingleton;

  /**
   * get hold of the singleton instance of FileUtil
   *
   * @return the singleton FileUtil
   */
  public static synchronized FileUtil instance() {
    if( fSingleton == null )
      fSingleton = new FileUtil();
    return fSingleton;
  }

  /**
   * read the supplied file in its entirety into a string
   *
   * @param the filename to read characters from
   * @return a string holding the file contents
   * @exception IOException reports problems that occurred
   */
  public String readCharacterFile( String fileName ) throws IOException {
    if( fileName == null )
      throw new IllegalArgumentException( "supplied filename to FileUtil was null" );
    return readCharacterFile( new FileReader( fileName ) );
  }

  /**
   * read the supplied file in its entirety into a string
   *
   * @param the file object to read characters from
   * @return a string holding the file contents
   * @exception IOException reports problems that occurred
   */
  public String readCharacterFile( File theFile ) throws IOException {
    if( theFile == null )
      throw new IllegalArgumentException( "supplied File object to FileUtil was null" );
    return readCharacterFile( new FileReader( theFile ) );
  }

  /**
   * read the supplied reader in its entirety into a string
   *
   * @param the Reader object to read characters from
   * @return a string holding the file contents
   * @exception IOException reports problems that occurred
   */
  public String readCharacterFile( Reader theReader ) throws IOException {
    if( theReader == null )
      throw new IllegalArgumentException( "supplied Reader object to FileUtil was null" );

    try {
      StringWriter sw = new StringWriter();
      char[] text = new char[kFILEBUFSIZE];
      int n;
      while( ( n = theReader.read( text, 0, kFILEBUFSIZE ) ) > 0 )
        sw.write( text, 0, n );

      return sw.toString();
    }
    finally {
      if( theReader != null )
        theReader.close();
    }
  }

  /**
   * write the supplied contents to the named file
   *
   * @param the filename to write string contents to
   * @param the file contents to be written
   * @exception IOException reports problems that occurred
   */
  public void writeCharacterFile( String fileName, String contents ) throws IOException {
    if( fileName == null )
      throw new IllegalArgumentException( "supplied filename to FileUtil was null" );
    writeCharacterFile( new FileWriter( fileName ), contents );
  }

  /**
   * write the supplied contents to the named file
   *
   * @param the File object to write string contents to
   * @param the file contents to be written
   * @exception IOException reports problems that occurred
   */
  public void writeCharacterFile( File file, String contents ) throws IOException {
    if( file == null )
      throw new IllegalArgumentException( "supplied File object to FileUtil was null" );
    writeCharacterFile( new FileWriter( file ), contents );
  }

  /**
   * write the supplied contents to the name file
   *
   * @param the Writer object to write string contents to
   * @param the file contents to be written
   * @exception IOException reports problems that occurred
   */
  public void writeCharacterFile( Writer fileWriter, String contents ) throws IOException {
    if( fileWriter == null )
      throw new IllegalArgumentException( "supplied FileWriter to FileUtil was null" );

    try {
      StringReader sr = new StringReader( contents );
      char[] text = new char[kFILEBUFSIZE];
      int n;
      while( ( n = sr.read( text, 0, kFILEBUFSIZE ) ) > 0 )
        fileWriter.write( text, 0, n );
    }
    finally {
      if( fileWriter != null )
        fileWriter.close();
    }
  }
}