FileInput类---载自《java软件开发》Russel Winder & Graham Roberts

import java.io.*;
/**
 *  A simple input class to read values from a file of characters.  If
 *  any file errors occur, methods in this class will display an error
 *  message and terminate the program.
 *
 *  @version 1.1 1999.09.10
 *  @author Graham Roberts
 *  @author Russel Winder
 */
public class FileInput {
  /**
   *  Instance variables to store the name of the file we are
   *  associated with.
   */
    private String filename = "";
    /**
     *  Instance variables for the filestream associated with the file
     *  that we are associated with.
     */
    private BufferedReader reader = null;
    /**
     *  Instance variables to store current state of EOF.
     */
    private boolean eof = false;
    /**
     *  Construct <CODE>FileInput</CODE> object given a file name.
     */
    public FileInput(final String fname) {
        filename = fname;
        try {
            reader = new BufferedReader(new FileReader(filename));
        }
        catch (FileNotFoundException e) {
            error("Can't open file: " + filename);
        }
    }
    /**
     *  Construct <CODE>FileInput</CODE> object given a
     *  <CODE>File</CODE> object.
     */
    public FileInput(final File file) {
        filename = file.getName();
        try {
            reader = new BufferedReader(new FileReader(file));
        }
        catch (FileNotFoundException e) {
            error("Can't open file: " + filename);
        }
    }
    /**
     *  Close the file when finished
     */
    public final synchronized void close() {
        try {
            reader.close();
        }
        catch(IOException e) {
            error("Can't close file: " + filename);
        }
    }
    /**
     *  Return true if the end of file has been reached.
     */
    public boolean eof() {
        return eof;
    }
    /**
     *  Read an <CODE>int</CODE> value from file.  The default
     *  return value is 0.
     */
    public final synchronized int readInteger() {
        String input = "";
        int value = 0;
        try {
            input = reader.readLine();
        }
        catch(IOException e) {
            error("readInteger failed for file: " + filename);
        }
        if(input == null) {
            eof = true;
        }
        else {
            try {
                value = Integer.parseInt(input);
            }
            catch(NumberFormatException e) {}
        }
        return value;
    }
    /**
     *  Read an <CODE>long</CODE> value from file.  The default
     *  return value is 0L.
     */
    public final synchronized long readLong() {
        String input = "";
        long value = 0L;
        try {
            input = reader.readLine();
        }
        catch(IOException e) {
            error("readLong failed for file: " + filename);
        }
        if(input == null) {
            eof = true;
        }
        else {
            try {
                value = Long.parseLong(input);
            }
            catch(NumberFormatException e) {}
        }
        return value;
    }
    /**
     *  Read an <CODE>double</CODE> value from file.  The default
     *  return value is 0.0.
     */
    public final synchronized double readDouble() {
        String input = "";
        double value = 0.0D;
        try {
            input = reader.readLine();
        }
        catch(IOException e) {
            error("readDouble failed for file: " + filename);
        }
        if(input == null) {
            eof = true;
        }
        else {
            try {
                value = Double.parseDouble(input);
            }
            catch(NumberFormatException e) {}
        }
        return value;
    }
    /**
     *  Read an <CODE>long</CODE> value from file.  The default
     *  return value is 0L.
     */
    public final synchronized float readFloat() {
        String input = "";
        float value = 0.0F;
        try {
            input = reader.readLine();
        }
        catch(IOException e) {
            error("readFloat failed for file: " + filename);
        }
        if(input == null) {
            eof = true;
        }
        else {
            try {
                value = Float.parseFloat(input);
            }
            catch(NumberFormatException e) {}
        }
        return value;
    }
    /**
     *  Read an <CODE>char</CODE> value from file.  The default
     *  return value is ' '(space)
     */
    public final synchronized char readCharacter() {
        char c = ' ';
        try {
            int n = reader.read();
            if (n == -1) {
                eof = true;
            }
            else {
                c = (char)n;
            }
        }
        catch (IOException e) {
            error("readCharacter failed for file: " + filename);
        }
        return c;
    }
    /**
     *  Read an <CODE>String</CODE> value from file.  The default
     *  return value is ""(the empty string).
     */
    public final synchronized String readString() {
        String s = "";
        try {
            s = reader.readLine();
        }
        catch (IOException e) {
            error("readString failed for file: " + filename);
        }
        if (s == null) {
            eof = true;
            s = "";
        }
        return s;
    }
    /**
     *  Deal with a file error, write a message and terminate.
     */
    private void error(String msg) {
        System.err.println(msg);
        System.err.println("Unable to continue executing program.");
        System.exit(0);
    }
}