Accessing a file and more.

Question

Hi, I have an encrypted text file. I need to do the following things within my program to make it useful.
1. Read the rather large 3.2MB file.
2. Decrypt the file, it is a simple translation of A = F, B = O etc.
3. Put each word into an ArrayList<String>.
I'm not sure where to start and this has been a bit of a stumbling block for me.

Answer 1

you might find read() useful.
package krc.utilz.io;
import java.util.Collection;
import java.util.List;
import java.util.ArrayList;
import java.util.Arrays;
import java.io.File;
import java.io.FileReader;
import java.io.BufferedReader;
import java.io.FileWriter;
import java.io.PrintWriter;
import java.io.InputStream;
import java.io.FileInputStream;
import java.io.Closeable;
import java.io.IOException;
import java.io.FileNotFoundException;
* @class: krc.utilz.io.Filez
* A collection of static "file handling" helper methods.
public abstract class Filez
  public static final int BFRSIZE = 4096;
   * reads the given file into one big string
   * @param String filename - the name of the file to read
   * @return the contents filename
  public static String read(String filename)
    throws IOException, FileNotFoundException
    FileReader in = null;
    StringBuffer out = new StringBuffer();
    try {
      in = new FileReader(filename);
      char[] cbuf = new char[BFRSIZE];
      int n = in.read(cbuf, 0, BFRSIZE);
      while(n > 0) {
        out.append(cbuf);
        n = in.read(cbuf, 0, BFRSIZE);
    } finally {
      if(in!=null)in.close();
    return out.toString();
  * a pseudonym for read especially for perl programmers
  public static String slurp(String filename)
    throws IOException, FileNotFoundException
    return(Filez.read(filename));
   * (re)writes the given content to the given filename
   * @param String content - the new contents of the fil
   * @param String filename - the name of the file to write.
  public static void write(String content, String filename)
    throws IOException
    PrintWriter out = null;
    try {
      out = new PrintWriter(new FileWriter(filename));
      out.write(content);
    } finally {
      if(out!=null)out.close();
  * a pseudonym for write especially for perl programmers
  public static void splooge(String content, String filename)
    throws IOException, FileNotFoundException
    Filez.write(content, filename);
   * reads each line of the given file into an array of strings.
   * @param String filename - the name of the file to read
   * @return a fixed length array of strings containing file contents.
  public  static String[] readArray(String filename)
    throws IOException, FileNotFoundException
    return readList(filename).toArray(new String[0]);
   * reads each line of the given file into an ArrayList of strings.
   * @param String filename - the name of the file to read
   * @return an ArrayList of strings containing file contents.
  public static ArrayList<String> readArrayList(String filename)
    throws IOException, FileNotFoundException
    return (ArrayList<String>)readList(filename);
   * reads each line of the given file into a List of strings.
   * @param String filename - the name of the file to read
   * @return an List handle ArrayList of strings containing file contents.
  public static List<String> readList(String filename)
    throws IOException, FileNotFoundException
    BufferedReader in = null;
    List<String> out = new ArrayList<String>();
    try {
      in = new BufferedReader(new FileReader(filename));
      String line = null;
      while ( (line = in.readLine()) != null ) {
          out.add(line);
    } finally {
      if(in!=null)in.close();
    return out;
   * reads the whole of the given file into an array of bytes.
   * @param String filename - the name of the file to read
   * @return an array of bytes containing the file contents.
  public static byte[] readBytes(String filename)
    throws IOException, FileNotFoundException
    return( readBytes(new File(filename)) );
   * reads the whole of the given file into an array of bytes.
   * @param File file - the file to read
   * @return an array of bytes containing the file contents.
  public static byte[] readBytes(File file)
    throws IOException, FileNotFoundException
    byte[] out = null;
    InputStream in = null;
    try {
      in = new FileInputStream(file);
      out = new byte[(int)file.length()];
      int size = in.read(out);
    } finally {
      if(in!=null)in.close();
    return out;
   * do files A & B have the same contents
   * @param String filenameA - the first file to compare
   * @param String filenameA - the second file to compare
   * @return boolean do-these-two-files-have-the-same-contents?
  public static boolean isSame(String filenameA, String filenameB)
    throws IOException, FileNotFoundException
    File fileA = new File(filenameA);
    File fileB = new File(filenameB);
    //check for same physical file
    if( fileA.equals(fileB) ) return(true);
    //compare sizes
    if( fileA.length() != fileB.length() ) return(false);
    //compare contents (buffer by buffer)
    boolean same=true;
    InputStream inA = null;
    InputStream inB = null;
    try {
      inA = new FileInputStream(fileA);
      inB = new FileInputStream(fileB);
      byte[] bfrA = new byte[BFRSIZE];
      byte[] bfrB = new byte[BFRSIZE];
      int sizeA=0, sizeB=0;
      do {
        sizeA = inA.read(bfrA);
        sizeB = inA.read(bfrB);
        if ( sizeA != sizeB ) {
          same=false;
        } else if ( sizeA == 0 ) {
          //do nothing
        } else if ( !Arrays.equals(bfrA,bfrB) ) {
          same=false;
      } while (same && sizeA != -1);
    } finally {
      if(inA!=null)inA.close();
      if(inB!=null)inB.close();
    return(same);
   * checks the given filename exists and is readable
   * @param String filename = the name of the file to "open".
   * @param OPTIONAl String type = a short name for the file used to identify
   *  the file in any exception messages.
   *  For example: "input", "input data", "DTD", "XML", or whatever.
   * @return a File object for the given filename.
   * @throw FileNotFoundException if the given file does not exist.
   * @throw IOException if the given file is unreadable (usually permits).
  public static File open(String filename)
    throws FileNotFoundException, IOException
    return(open(filename,"input"));
  public static File open(String filename, String type)
    throws FileNotFoundException, IOException
    File file = new File(filename);
    String fullname = file.getCanonicalPath();
    if(!file.exists()) throw new FileNotFoundException(type+" file does not exist: "+fullname);
    if(!file.canRead()) throw new IOException(type+" file is not readable: "+fullname);
    return(file);
   * gets the filename-only portion of a canonical-filename, with or without
   * the extension.
   * @param String path - the full name of the file.
   * OPTIONAL @param boolean cutExtension - if true then remove any .ext
   * @return String the filename-only (with or without extension)
  public static String basename(String path) {
    return(basename(path,false));
  public static String basename(String path, boolean cutExtension)
    String fname = (new File(path)).getName();
    if (cutExtension) {
      int i = fname.lastIndexOf(".");
      if(i>0) fname = fname.substring(0,i);
    return(fname);
   * gets the directory portion of a canonical-filename
   * @param String path - the full name of the file.
   * @return String the parent directory of the given path.
  public static String dirname(String path)
    return( new File(path).getParent() );
   * close these "streams"
   * @param Closeable... "streams" to close.
  public static void close(Closeable... streams) {
    for(Closeable stream : streams) {
      if(stream==null) continue;
      try {
        stream.close();
      } catch (Exception e) {
        System.err.println(e);
}