textio.java

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         catch (Exception e) {
         }
      }
      out = newout;
      writingStandardOutput = false;
      outputFileName = selectedFile.getName();
      outputErrorCount = 0;
      return true;
   }
   

   /**
    * If TextIO is currently reading from a file, then the return value is the name of the file.  
    * If the class is reading from standard input or from a stream, then the return value is null.
    */
   public static String getInputFileName() {
      return inputFileName;
   }
   

   /**
    * If TextIO is currently writing to a file, then the return value is the name of the file.  
    * If the class is writing to standard output or to a stream, then the return value is null.
    */
   public static String getOutputFileName() {
      return outputFileName;
   }
   

   // *************************** Output Methods *********************************
      
   /**
    * Write a single value to the current output destination, using the default format
    * and no extra spaces.  This method will handle any type of parameter, even one
    * whose type is one of the primitive types.
    */
   public static void put(Object x) { 
      out.print(x); 
      out.flush();
      if (out.checkError())
         outputError("Error while writing output.");
   }
   
   /**
    * Write a single value to the current output destination, using the default format
    * and outputting at least minChars characters (with extra spaces added before the
    * output value if necessary).  This method will handle any type of parameter, even one
    * whose type is one of the primitive types.
    * @param x The value to be output, which can be of any type.
    * @param minChars The minimum number of characters to use for the output.  If x requires fewer
    * then this number of characters, then extra spaces are added to the front of x to bring
    * the total up to minChars.  If minChars is less than or equal to zero, then x will be printed
    * in the minumum number of spaces possible.
    */
   public static void put(Object x, int minChars)  { 
      if (minChars <= 0)
         out.print(x);
      else {
         out.printf("%" + minChars + "s", x);
         out.flush();
      }
      if (out.checkError())
         outputError("Error while writing output.");
   }
      
   /**
    * This is equivalent to put(x), followed by an end-of-line.
    */
   public static void putln(Object x) { 
      out.println(x);
      out.flush();
      if (out.checkError())
         outputError("Error while writing output.");
   }
   
   /**
    * This is equivalent to put(x,minChars), followed by an end-of-line.
    */
   public static void putln(Object x, int minChars) {
      put(x,minChars);
      out.println();
      out.flush();
      if (out.checkError())
         outputError("Error while writing output.");
   }

   /**
    * Write an end-of-line character to the current output destination.
    */
   public static void putln() {
      out.println();
      out.flush();
      if (out.checkError())
         outputError("Error while writing output.");
   }
   
   /**
    * Writes formatted output values to the current output destination.  This method has the
    * same function as System.out.printf(); the details of formatted output are not discussed
    * here.  The first parameter is a string that describes the format of the output.  There
    * can be any number of additional parameters; these specify the values to be output and
    * can be of any type.  This method will throw an IllegalArgumentException if the
    * format string is null or if the format string is illegal for the values that are being
    * output.
    */
   public static void putf(String format, Object... items) {
      if (format == null)
         throw new IllegalArgumentException("Null format string in TextIO.putf() method.");
      try {
         out.printf(format,items);
      }
      catch (IllegalFormatException e) {
         throw new IllegalArgumentException("Illegal format string in TextIO.putf() method.");
      }
      out.flush();
      if (out.checkError())
         outputError("Error while writing output.");
   }
   
   // *************************** Input Methods *********************************

   /**
    * Test whether the next character in the current input source is an end-of-line.  Note that
    * this method does NOT skip whitespace before testing for end-of-line -- if you want to do
    * that, call skipBlanks() first.
    */
   public static boolean eoln() { 
      return peek() == '\n'; 
   }

   /**
    * Test whether the next character in the current input source is an end-of-file.  Note that
    * this method does NOT skip whitespace before testing for end-of-line -- if you want to do
    * that, call skipBlanks() or skipWhitespace() first.
    */
   public static boolean eof()  { 
      return peek() == EOF; 
   }
   
   /**
    * Reads the next character from the current input source.  The character can be a whitespace
    * character; compare this to the getChar() method, which skips over whitespace and returns the
    * next non-whitespace character.  An end-of-line is always returned as the character '\n', even
    * when the actual end-of-line in the input source is something else, such as '\r' or "\r\n".
    * This method will throw an IllegalArgumentException if the input is at end-of-file (which will 
    * not ordinarily happen if reading from standard input).
    */
   public static char getAnyChar() { 
      return readChar(); 
   }

   /**
    * Returns the next character in the current input source, without actually removing that
    * character from the input.  The character can be a whitespace character and can be the
    * end-of-file character (specfied by the constant TextIO.EOF).An end-of-line is always returned 
    * as the character '\n', even when the actual end-of-line in the input source is something else, 
    * such as '\r' or "\r\n".  This method never causes an error.
    */
   public static char peek() { 
      return lookChar();
   }
   
   /**
    * Skips over any whitespace characters, except for end-of-lines.  After this method is called,
    * the next input character is either an end-of-line, an end-of-file, or a non-whitespace character.
    * This method never causes an error.  (Ordinarly, end-of-file is not possible when reading from
    * standard input.)
    */
   public static void skipBlanks() { 
      char ch=lookChar();
      while (ch != EOF && ch != '\n' && Character.isWhitespace(ch)) {
         readChar();
         ch = lookChar();
      }
   }

   /**
    * Skips over any whitespace characters, including for end-of-lines.  After this method is called,
    * the next input character is either an end-of-file or a non-whitespace character.
    * This method never causes an error. (Ordinarly, end-of-file is not possible when reading from
    * standard input.)
    */
   private static void skipWhitespace() {
      char ch=lookChar();
      while (ch != EOF && Character.isWhitespace(ch)) {
         readChar();
         if (ch == '\n' && readingStandardInput && writingStandardOutput) {
            out.print("? ");
            out.flush();
         }
         ch = lookChar();
      }
   }

   /**
    * Skips whitespace characters and then reads a value of type byte from input, discarding the rest of 
    * the current line of input (including the next end-of-line character, if any).  When using standard IO,
    * this will not produce an error; the user will be prompted repeatedly for input until a legal value
    * is input.  In other cases, an IllegalArgumentException will be thrown if a legal value is not found.
    */
   public static byte getlnByte() { 
      byte x=getByte(); 
      emptyBuffer(); 
      return x; 
   }
   
   /**
    * Skips whitespace characters and then reads a value of type short from input, discarding the rest of 
    * the current line of input (including the next end-of-line character, if any).  When using standard IO,
    * this will not produce an error; the user will be prompted repeatedly for input until a legal value
    * is input.  In other cases, an IllegalArgumentException will be thrown if a legal value is not found.
    */
   public static short getlnShort() {
      short x=getShort();
      emptyBuffer(); 
      return x; 
   }
   
   /**
    * Skips whitespace characters and then reads a value of type int from input, discarding the rest of 
    * the current line of input (including the next end-of-line character, if any).  When using standard IO,
    * this will not produce an error; the user will be prompted repeatedly for input until a legal value
    * is input.  In other cases, an IllegalArgumentException will be thrown if a legal value is not found.
    */
   public static int getlnInt() { 
      int x=getInt(); 
      emptyBuffer(); 
      return x; 
   }
   
   /**
    * Skips whitespace characters and then reads a value of type long from input, discarding the rest of 
    * the current line of input (including the next end-of-line character, if any).  When using standard IO,
    * this will not produce an error; the user will be prompted repeatedly for input until a legal value
    * is input.  In other cases, an IllegalArgumentException will be thrown if a legal value is not found.
    */
   public static long getlnLong() {
      long x=getLong(); 
      emptyBuffer(); 
      return x;
   }
   
   /**
    * Skips whitespace characters and then reads a value of type float from input, discarding the rest of 
    * the current line of input (including the next end-of-line character, if any).  When using standard IO,
    * this will not produce an error; the user will be prompted repeatedly for input until a legal value
    * is input.  In other cases, an IllegalArgumentException will be thrown if a legal value is not found.
    */
   public static float getlnFloat() {
      float x=getFloat(); 
      emptyBuffer(); 
      return x;
   }
   
   /**
    * Skips whitespace characters and then reads a value of type double from input, discarding the rest of 
    * the current line of input (including the next end-of-line character, if any).  When using standard IO,
    * this will not produce an error; the user will be prompted repeatedly for input until a legal value
    * is input.  In other cases, an IllegalArgumentException will be thrown if a legal value is not found.
    */
   public static double getlnDouble() { 
      double x=getDouble(); 
      emptyBuffer(); 
      return x; 
   }
   
   /**
    * Skips whitespace characters and then reads a value of type char from input, discarding the rest of 
    * the current line of input (including the next end-of-line character, if any).  Note that the value
    * that is returned will be a non-whitespace character; compare this with the getAnyChar() method.
    * When using standard IO, this will not produce an error.  In other cases, an error can occur if
    * an end-of-file is encountered.
    */
   public static char getlnChar() {
      char x=getChar(); 
      emptyBuffer(); 
      return x;
   }
   
   /**
    * Skips whitespace characters and then reads a value of type boolean from input, discarding the rest of 
    * the current line of input (including the next end-of-line character, if any).  When using standard IO,
    * this will not produce an error; the user will be prompted repeatedly for input until a legal value
    * is input.  In other cases, an IllegalArgumentException will be thrown if a legal value is not found.
    * <p>Legal inputs for a boolean input are: true, t, yes, y, 1, false, f, no, n, and 0; letters can be
    * either upper case or lower case. One "word" of input is read, using the getWord() method, and it
    * must be one of these; note that the "word"  must be terminated by a whitespace character (or end-of-file).
    */
   public static boolean getlnBoolean() { 
      boolean x=getBoolean(); 
      emptyBuffer();
      return x; 
   }
   
   /**
    * Skips whitespace characters and then reads one "word" from input, discarding the rest of 
    * the current line of input (including the next end-of-line character, if any).  A word is defined as
    * a sequence of non-whitespace characters (not just letters!).   When using standard IO,
    * this will not produce an error.  In other cases, an IllegalArgumentException will be thrown
    * if an end-of-file is encountered.
    */
   public static String getlnWord() {
      String x=getWord(); 
      emptyBuffer(); 
      return x; 
   }
   
   /**
    * This is identical to getln().
    */
   public static String getlnString() {
      return getln();
   } 
   
   /**
    * Reads all the charcters from the current input source, up to the next end-of-line.  The end-of-line
    * is read but is not included in the return value.  Any other whitespace characters on the line are retained,
    * even if they occur at the start of input.  The return value will be an empty string if there are no
    * no characters before the end-of-line.  When using standard IO, this will not produce an error.  
    * In other cases, an IllegalArgumentException will be thrown if an end-of-file is encountered.
    */
   public static String getln() {
      StringBuffer s = new StringBuffer(100);
      char ch = readChar();
      while (ch != '\n') {
         s.append(ch);
         ch = readChar();
      }
      return s.toString();
   }