Java Programming Streams and Files

1
Java Programming Streams and Files

• Streams and Files
• Provided by the java.io package for handling
  input/output
• InputStream
• An abstract class representing an input stream of
  bytes. All InputStreams are based on this class.
• Methods(some of)
• available() close() read() read(byte)
  mark(int) reset() skip(long)
• OutputStream
• Abstract class representing an output stream of
  bytes. All OutputStreams are based on this class.
  
• Methods(some of)
• close() write(int) write(byte) write(byte,
  int, int) flush()

2
Java Programming Streams and Files

• PrintStream - Used for "ascii" output
• System.out is a printstream
• class PrintStreamExample
• public static void main( String args )
• System.out.println( "Hi Dad" )
• Constructors
• PrintStream(OutputStream) - Creates a new
  PrintStream.
• PrintStream(OutputStream, boolean) - Creates a
  new PrintStream, with auto flushing.
• PrintStream Methods
• checkError() print(int) println(double) close()
  flush print(long) println(float) print(Object)
• println(int) print(boolean) print(String)
  println(long) print(char) println()
  println(Object)
• print(char) println(boolean)
  println(String) print(double) println(char)
  write(byte, int, int)
• print(float) println(char) write(int)

3
Java Programming Streams and Files

• File
• Represents a file or directory name in a
  platform-independent way
• Constructors File(String)
• Creates a File object.
• File(String, String) - Creates a File object from
  the specified directory.
• File(File, String) - Creates a File object
  (given a directory File object).
• (Note. See FileReader and FileWriter in later
  versions of Java)
• File Methods
• canRead() getParent() length() canWrite()
  getPath() list() delete() hashCode()
• list(FilenameFilter) equals(Object) exists()
  isAbsolute() mkdir() isDirectory() mkdirs()
  getAbsolutePath() isFile() renameTo(File)
  getName() lastModified() toString()

4
Java Programming Streams and Files

• Example
• import java.io.
• class FileExamples
• public static void main( String args )
• // New files
• File classDirectory new File(
  "ac461" )
• classDirectory.mkdir()
  // Did not exist prior
• File gradeFile new File( "ac461",
  "grades.text" )
• gradeFile.mkdir()
  // Did not exist prior
• File lectureNotes new File(
  "ac461/lectures.text" )
• lectureNotes.mkdir()
  // Did not exist prior
• String fileList classDirectory.list()
• for ( int fileNum 0 fileNum lt
  fileList.length fileNum )
• System.out.print( fileList fileNum
  "\t" )
• System.out.println()
• // Output
• // grades.text lectures.text

5
Java Programming Streams and Files

• FileInputStream
• File input stream, can be constructed from a file
  descriptor or a file name.
• Constructors
• FileInputStream(String) - Creates an input file
  with the specified system dependent file name.
• FileInputStream(File) - Creates an input file
  from the specified File object.
• FileInputStream(FileDescriptor)
• FileInputStream Methods
• available() read() close() read(byte)
• finalize() read(byte, int, int) getFD()
  skip(long)

6
Java Programming Streams and Files

• FileOutputStream
• File output stream, can be constructed from a
  file descriptor or a file name.
• Constructors
• FileOutputStream(String) - Creates an output file
  with the specified system dependent file name.
• FileOutputStream(File) - Creates an output file
  with the specified File object.
• FileOutputStream(FileDescriptor)
• FileOutputStream Methods
• close() write(byte) finalize() write(byte,
  int, int) getFD() write(int)

7
Java Programming Streams and Files

• DataInputStream
• Provides methods to read all the standard types
  from a byte-oriented InputStream
• readBoolean readByte readShort readInt
  readLong readFloat
• readChar readUTF readLine(deprecated)
• DataOutputStream
• Provides methods to write all of the primitive
  language types over a byte-oriented OutputStream
• writeBooleanl writeByte writeShort writeInt
  writeLong writeFloat
• writeChar writeUTF

8
Java Programming Streams and Files

• Java 2 (additions)
• Reader(abstract class for reading character
  streams)
• BufferedReader
• read (reads one or more characters)
• readLine(reads a line of text)
• InputStreamReader(bridge from byte to character
  streams)
• StringReader(character stream whose source is a
  string)
• FileReader (accessing a file)
• Writer (abstract class for writing to character
  streams)
• BufferedWriter
• write(writes one or more characters)
• newLine() (line separator)
• OutputStreamWriter(bridge from character streams
  to byte streams)
• PrintWriter (print formatted representations of
  objects to text output
• print println write
• FileWriter

9
Java Programming Streams and Files

• Example - reading file
• import java.io.
• class ReadingFileExample
• public static void main( String args )
  throws Exception
• FileReader sourceFile new
  FileReader( "ReadingFileExample.java" )
• BufferedReader inputFile new
  BufferedReader( sourceFile)
• for ( int k 1 k lt 10 k )
• System.out.println(
  inputFile..readLine() )
• DataInputStream inputFileFormatted new
  DataInputStream(inputFile)
• System.out.println(inputFileFormatted.readInt()
  )

10
Java Programming Streams and Files

• Example - writing to file
• import java.io.
• class WritingToFile
• public static void main( String args )
  throws Exception
• int x7
• String name Tom Jones
• FileWriter writeFile new FileWriter(
  "newFile.txt")
• BufferedWriter bufferedWriteFile new
  BufferedWriter ( writeFile )
• PrintWriter out new PrintWriter(
  bufferedWriteFile)
• out.println(x)
• out.println(name)
• out.write( "Distributed Computing")