CS535 Object-Oriented Programming & Design
Fall Semester, 1996
IO & Streams

1. References
2. The I/O Package
   1. InputStream
   2. OutputStream
   3. PrintStream
   4. FileInputStream
   5. FileOutputStream
   6. ASCIIInputStream
   7. Combining InputStreams
   8. Combining OutputStreams
   9. File
   10. StreamTokenizer
       1. Some Real Parsing

Doc 14, IO & Streams Slide # 1

Peter Williams

---

Doc 14, IO & Streams Slide # 2

A source (input streams) or

A destination (output stream)

FileInputStream

FileOutputStream

Doc 14, IO & Streams Slide # 3

---

Doc 14, IO & Streams Slide # 4

Useful in communications between threads

Read/write byte arrays

Abstract classes, filter bytes from another stream

Can be chained together

Adds buffering

Reads/writes built-in types (int, float, etc )

Steam stores types in binary not ASCII or Unicode

Used for file IO

Doc 14, IO & Streams Slide # 5

Returns the number of bytes that can be read without blocking.

Closes the input stream.

Marks the current position in the input stream.

Returns a boolean indicating whether or not this stream type supports mark/reset.

Doc 14, IO & Streams Slide # 6

Reads a byte of data, but returns an int

Reads into an array of bytes.

Reads into an array of bytes.

Repositions the stream to the last marked position.

Skips n bytes of input.

Doc 14, IO & Streams Slide # 7

class  CountSize  
   {
   public static void main( String args[] ) throws IOException, 
                              FileNotFoundException
      {
      try
         {
         InputStream in = new FileInputStream( "Exam" );
         
         int total;
         
         for ( total = 0; in.read() != -1; total++)
            ;
         
         System.out.println( total );
         }
      catch ( FileNotFoundException fileProblem )
         {
         System.err.println( "File not found" );
         throw fileProblem;
         }
      catch ( IOException ioProblem )
         {
         System.err.println( "IO problem" );
         throw ioProblem;
      
         }
      }
   }

Doc 14, IO & Streams Slide # 8

read() returns -1 if end of stream is reached, else returns the next byte

class  Read  
   {
   public static void main( String args[] ) throws IOException
      {
      InputStream in
      in = new StringBufferInputStream( "abcdefghij" );
      
      System.out.println( in.read() + " raw read, ascii value " );
      System.out.println( (char) in.read() + " cast read to char " );
      
      }
   }

Doc 14, IO & Streams Slide # 9

Closes the stream

Flushes the stream

Writes an array of bytes

Writes a sub array of bytes

Writes a byte

Doc 14, IO & Streams Slide # 10

class  CountSize  
   {
   public static void main( String args[] ) throws IOException
      {
      InputStream in;
      in = new StringBufferInputStream( "abcdefghij" );

      OutputStream out = System.out;
      
      int nextChar;
      
      while ( ( nextChar = in.read() ) != -1  )
         out.write(  Character.toUpperCase( (char) nextChar ) );

      out.write( '\n' );
      out.flush();
      }
   }

Doc 14, IO & Streams Slide # 11

class  PrintStreamExample
   {
   public  static  void  main( String  args[] )
      {
      System.out.println(  "Hi Mom"  );
      }
   }

Creates a new PrintStream.

Creates a new PrintStream, with auto flushing.

Flushes the print stream and returns whether or not there was an error on the output stream.

Doc 14, IO & Streams Slide # 12

   public void write(int b) 
   {
   try 
      {
      out.write(b);
      if (autoflush && (b == '\n')) 
         {
         out.flush();
         }
      } 
   catch (InterruptedIOException ex) 
      {
      // We've been interrupted.  Make sure we're still interrupted.
      Thread.currentThread().interrupt();
      } 
   catch (IOException ex) 
      {
      trouble = true;
      }
    }

Doc 14, IO & Streams Slide # 13

class  PoorPrint
   {
   String  name  =  "sam";
   }

class  FancyPrint
   {
   String  name  =  "pete";

   public  String  toString()
      {
      return  "FancyPrint( "  +  name  +  " )";
      }
   }

class  TestPrint
   {
   public  static  void  main( String  args[]  )
      {
      PoorPrint  outOfIt  =  new  PoorPrint();
      FancyPrint  cool  =  new FancyPrint();

      System.out.println(  outOfIt  );
      System.out.println( cool  );
      }
   }

Doc 14, IO & Streams Slide # 14

public void print( Object obj ) 
   {
   print(  String.valueOf( obj ) );
   }

public static String valueOf(Object obj) 
   {
   return (obj == null) ? "null" : obj.toString();
   }

Doc 14, IO & Streams Slide # 15

Creates an input file with the specified system dependent file name.

Creates an input file from the specified File object.

Doc 14, IO & Streams Slide # 16

Creates an output file with the specified system dependent file name.

Creates an output file with the specified File object.

Doc 14, IO & Streams Slide # 17

Creates a new ASCIIInputStream.

Doc 14, IO & Streams Slide # 18

import java.io.*;
import sdsu.io.*;
class  ReadingFileExample
   {
   public  static  void  main( String  args[]  ) throws Exception
      {
      FileInputStream inputFile;
      BufferedInputStream bufferedFile;
      ASCIIInputStream  cin;
      
      inputFile = new FileInputStream( "ReadingFileExample.java" );
      bufferedFile = new BufferedInputStream( inputFile );
      cin = new ASCIIInputStream( bufferedFile );

      System.out.println(  cin.readWord()  );

      for  ( int  k = 1 ;  k  <  4;  k++ )
         System.out.println(  cin.readLine()  );
      }
   }

import
 sdsu.io.*;
import java.io.*;
class  ReadingFileExample
Doc 14, IO & Streams Slide # 19

public  static  void  main( String  args[]  ) throws Exception
   {
   InputStream input;
   ASCIIInputStream  cin;
   
   input = new StringBufferInputStream( "hi mom how is dad?" );
   input = new UpperCaseInputStream( input );   
   cin = new ASCIIInputStream( input );

   System.out.println(  cin.readWord()  );
   System.out.println(  cin.readLine()  );
   

HI
 MOM HOW IS DAD?
Doc 14, IO & Streams Slide # 20

class  UpperCaseInputStream extends FilterInputStream 
   {
   public static final int EOF = -1;
   
   public UpperCaseInputStream( InputStream input )
      {
      super( input );  // input is stored in field "in"
      }
      
   public int read() throws IOException
      {
      int nextChar = in.read();
      if ( nextChar == EOF )
         return EOF;
      else
         return toUpperCase( (char) nextChar );
      }
   
   public int read(byte bytes[], int offset, int length) throws 
                                    IOException 
      {
      int charsRead = in.read(bytes, offset, length);
      
      if ( charsRead == EOF )
         return EOF;
         
      for ( int index = offset; index < offset + charsRead; index++)
         bytes[ index ] = toUpperCase( (char) bytes[ index ] ) ;
      
      return charsRead;
      }

   protected byte toUpperCase( char convertMe ) {
      return (byte) Character.toUpperCase(  convertMe );
      }
   }

Doc 14, IO & Streams Slide # 21

import java.io.*;
class  WritingToFileExample
   {
   public  static  void  main( String  args[]  ) throws Exception
      {
      FileOutputStream outputFile;
      BufferedOutputStream bufferedFile;
      PrintStream   cout;
      
      outputFile = new FileOutputStream( "LetterHome" );
      bufferedFile = new BufferedOutputStream( outputFile );
      cout = new PrintStream( bufferedFile );
      
      cout.println( "Hi Mom" );
      cout.println( "How is Dad?" );
      cout.flush();
      cout.close();
      }
   }
Doc 14, IO & Streams Slide # 22

Doc 14, IO & Streams Slide # 23

import java.io.*;
class  FileExamples {
   public  static  void  main( String  args[]  )
      {
      // New files
      File  classDirectory  =  new File(  "cs596"  );
      classDirectory.mkdir();         // Did not exist prior

      File  gradeFile  =  new File( "cs596", "grades.text"  );
      gradeFile.mkdir();            // Did not exist prior

      File  lectureNotes  =  new File( "cs596/lectures.text" );
      lectureNotes.mkdir();            // Did not exist prior

      // Existing file
      File  sourceFile  =  new File( "FileExamples.java" );

      String[]  fileList  =  classDirectory.list();
      for (  int fileNum = 0;  fileNum < fileList.length; fileNum++ )
         System.out.print(  fileList[ fileNum ] + "\t" );
      System.out.println();

      System.out.println(  classDirectory.getAbsolutePath()  );
      System.out.println(  gradeFile.exists()  );
      System.out.println(  gradeFile.getParent()  );
      System.out.println(  sourceFile.length()  );
      System.out.println(  sourceFile.lastModified()  );
      gradeFile.delete();
      }
   }

grades.text     lectures.text
/home/ma/whitney/java/notes/cs596
true
cs596
980
823933450000
Doc 14, IO & Streams Slide # 24

import java.io.*;

class  MakeDirectoriesExamples
   {
   public  static  void  main( String  args[]  )
      {

      // Does nothing if test/this does not exist
      File  a  =  new File(  "test/this/out"  );
      a.mkdir();


      // creates all four directories 
      File  b  =  new File( "second/test/of/this"  );
      b.mkdirs();
      }
   }


import java.io.*;
class  MachineIndependentFileNames
   {
   public  static  void  main( String  args[]  )
      {
      String  gradeFile  =  "/home/ma/whitney/cs596/grades";
      gradeFile  =  gradeFile.replace( '/', File.separatorChar );
      System.out.println(  gradeFile  );
      }
   }
Doc 14, IO & Streams Slide # 25

More complex than the StringTokenizer

Designed to parse "Java-style" input

Parses numbers

Parses Java-style comments

Doc 14, IO & Streams Slide # 26

sval for string (or word )

nval for number (declared a double not Double)

A string (word) was scanned

The string field sval contains the word scanned

A number was scanned

Only decimal floating-point numbers (with or without a decimal point) are recognized

End-of-line scanned

End-of-file scanned

Doc 14, IO & Streams Slide # 27

import java.io.*;

class  Tokenizer  
   {
   public static void main( String args[] ) throws Exception 
      {
      String sample = "this 123 is an 3.14 \n simple test";
      InputStream in;
      in = new StringBufferInputStream( sample );
      StreamTokenizer parser = new StreamTokenizer( in );
      
      while ( parser.nextToken() != StreamTokenizer.TT_EOF )
         {
         if ( parser.ttype == StreamTokenizer.TT_WORD)
            System.out.println( "A word: " + parser.sval );
         else if  ( parser.ttype == StreamTokenizer.TT_NUMBER )
            System.out.println( "A number: " + parser.nval );
         else if  ( parser.ttype == StreamTokenizer.TT_EOL )
            System.out.println( "EOL" );
         else
            System.out.println( "Other: " + (char) parser.ttype );
         }   
      }
   }

Doc 14, IO & Streams Slide # 28

Characters that are treated special

White space

Characters that make up numbers

Characters that make up words (tokens)

All nonspecial characters

a - z

A - Z

ascii values 130 through 255

ascii values 0 through 32

includes space, tab, line feed, carriage return, escape

Doc 14, IO & Streams Slide # 29

  public void resetSyntax()

       Resets the syntax table so that all characters are special. 

  public void resetSyntax()

       Resets the syntax table so that all characters are special. 

  public void resetSyntax()

       Resets the syntax table so that all characters are ordinary. 

Doc 14, IO & Streams Slide # 30

import java.io.*;

class  Tokenizer  
   {
   public static void main( String args[] ) throws Exception 
      { 
      String sample = "this 123 is an 3.14 \n simple test";
      InputStream in =  new StringBufferInputStream( sample );
      StreamTokenizer parser = new StreamTokenizer( in );
      parser.eolIsSignificant( true ); 
      
      while ( parser.nextToken() != StreamTokenizer.TT_EOF )
         {
         if ( parser.ttype == StreamTokenizer.TT_WORD)
            System.out.println( "A word: " + parser.sval );
         else if  ( parser.ttype == StreamTokenizer.TT_NUMBER )
            System.out.println( "A number: " + parser.nval );
         else if  ( parser.ttype == StreamTokenizer.TT_EOL )
            System.out.println( "EOL" );
         else
            System.out.println( "Other: " + (char) parser.ttype );
         }   
      }
   }

Doc 14, IO & Streams Slide # 31

import java.io.*;

class  Tokenizer  
   {
   public static void main( String args[] ) throws Exception 
      { 
      String sample = "this 123 /is an 3.14 \n simple test";

      InputStream in = new StringBufferInputStream( sample );
      StreamTokenizer parser = new StreamTokenizer( in );
      
      while ( parser.nextToken() != StreamTokenizer.TT_EOF )
         {
         if ( parser.ttype == StreamTokenizer.TT_WORD)
            System.out.println( "A word: " + parser.sval );
         else if  ( parser.ttype == StreamTokenizer.TT_NUMBER )
            System.out.println( "A number: " + parser.nval );
         else if  ( parser.ttype == StreamTokenizer.TT_EOL )
            System.out.println( "EOL" );
         else
            System.out.println( "Other: " + (char) parser.ttype );
         }   
      }
   }

Doc 14, IO & Streams Slide # 32

import java.io.*;
class  Tokenizer  
   {
   public static void main( String args[] ) throws Exception 
      { 
      String sample = "this #123 /is an 3.14# \n simple test";

      InputStream in = new StringBufferInputStream( sample );
      StreamTokenizer parser = new StreamTokenizer( in );

      parser.quoteChar( '#' );

      while ( parser.nextToken() != StreamTokenizer.TT_EOF )
         {
         if ( parser.ttype == StreamTokenizer.TT_WORD)
            System.out.println( "A word: " + parser.sval );
         else if  ( parser.ttype == StreamTokenizer.TT_NUMBER )
            System.out.println( "A number: " + parser.nval );
         else if  ( parser.ttype == StreamTokenizer.TT_EOL )
            System.out.println( "EOL" );
         else
            System.out.println( "Other: " + (char) parser.ttype +
                           "sval: " + parser.sval );
         }   
      }
   }

Doc 14, IO & Streams Slide # 33

import java.io.*;
class  Tokenizer  
   {
   public static void main( String args[] ) throws Exception 
      { 
      String sample = "this #123 /is an 3.14 \n simple # test";

      InputStream in = new StringBufferInputStream( sample );
      StreamTokenizer parser = new StreamTokenizer( in );

      parser.quoteChar( '#' );

      while ( parser.nextToken() != StreamTokenizer.TT_EOF )
         {
         if ( parser.ttype == StreamTokenizer.TT_WORD)
            System.out.println( "A word: " + parser.sval );
         else if  ( parser.ttype == StreamTokenizer.TT_NUMBER )
            System.out.println( "A number: " + parser.nval );
         else if  ( parser.ttype == StreamTokenizer.TT_EOL )
            System.out.println( "EOL" );
         else
            System.out.println( "Other: " + (char) parser.ttype +
                           "sval: " + parser.sval );
         }   
      }
   }

Doc 14, IO & Streams Slide # 34

import java.io.*;
class  Tokenizer  {
   public static void main( String args[] ) throws Exception { 

      String sample = "this #123 /is an 3.14 \n simple # test";

      InputStream in = new StringBufferInputStream( sample );
      StreamTokenizer parser = new StreamTokenizer( in );

      parser.wordChars( 0, 255 );
      parser.ordinaryChar( 's' );

      while ( parser.nextToken() != StreamTokenizer.TT_EOF )
         {
         if ( parser.ttype == StreamTokenizer.TT_WORD)
            System.out.println( "A word: " + parser.sval );
         else if  ( parser.ttype == StreamTokenizer.TT_NUMBER )
            System.out.println( "A number: " + parser.nval );
         else if  ( parser.ttype == StreamTokenizer.TT_EOL )
            System.out.println( "EOL" );
         else
            System.out.println( "Other: " + (char) parser.ttype +
                           "sval: " + parser.sval );
         }   
      }
   }

A word: thi
Other: ssval: null
A word: #123 /i
Other: ssval: null
A word: an 3.14 
 
Other: ssval: null
A word: imple # te
Other: ssval: null
A word: t
Doc 14, IO & Streams Slide # 35

class  Tokenizer  
   {
   public static void main( String args[] ) throws Exception 
      { 

      String sample = "name=value; sam = \n A";

      InputStream in = new StringBufferInputStream( sample );
      StreamTokenizer parser = new StreamTokenizer( in );

      parser.wordChars( 0, 255 );
      parser.whitespaceChars( 0, 32 );
      parser.ordinaryChar( ';' );
      parser.ordinaryChar( '=' );

      while ( parser.nextToken() != StreamTokenizer.TT_EOF )
         {
         if ( parser.ttype == StreamTokenizer.TT_WORD)

         // same as previous examples
         }   
      }
   }

Doc 14, IO & Streams Slide # 36

class  Tokenizer  
   {
   public static void main( String args[] ) throws Exception 
      { 
      String sample = "name with space=value # a commment\n; "
                     + " 'sam =cat' = \n A";

      InputStream in = new StringBufferInputStream( sample );
      StreamTokenizer parser = new StreamTokenizer( in );

      parser.wordChars( 0, 255 );
      parser.whitespaceChars( 9, 13 ); //tab, line feed, return
      parser.ordinaryChar( ';' );
      parser.ordinaryChar( '=' );
      parser.commentChar( '#' );
      parser.quoteChar( '\'' );

      while ( parser.nextToken() != StreamTokenizer.TT_EOF )
         {
         // Same as other examples
         }   
      }
   }

Doc 14, IO & Streams Slide # 37

   public static void main( String args[] ) throws Exception 
      { 
      String sample = "name;with;space=value # a commment\n; "
                     + "sam & cat = \n A";
      InputStream in = new StringBufferInputStream( sample );
      StreamTokenizer parser = new StreamTokenizer( in );

      parser.wordChars( 0, 255 );
      parser.whitespaceChars( 9, 13 ); //tab, line feed, return
      parser.ordinaryChar( '=' );
      parser.commentChar( '#' );

      while ( parser.nextToken() != StreamTokenizer.TT_EOF )
         {
         if ( parser.ttype == StreamTokenizer.TT_WORD)
            System.out.println( "A word: " + parser.sval );
         else if  ( parser.ttype == '=' )
            {
            System.out.println( "=: ");
            parser.ordinaryChar( ';' );
            parser.wordChars( '=', '=' );
            }
         else if  ( parser.ttype == ';' )
            {
            System.out.println( ";: " );
            parser.ordinaryChar( '=' );
            parser.wordChars( ';', ';' );
            }
         else
            System.out.println( "Error: " + (char) parser.ttype +
                           "sval: " + parser.sval );
         }   
      }