Lecture 23


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Lecture 23

  1. 1. Core Java Debasish Pratihari Concept of Stream :   In file processing, input refers to the flow of data into a program and output means the flow of data out of the program. Java uses the concept of streams to represent the ordered sequence of data. A stream presents a uniform, easy-to-use, object-oriented interface between the program and the input/output devices. A stream in java is a path along which data flows. It has a source and a destination and it supports unidirectional movement of data. Note : Streams can be visualized as a sequence of data. Input/Output Operations Keyboard Screen Printer Mouse Memory Java Program Memory Disk Disk Network Network Streams in Java Note : Java streams are classified into two basic types  InputStream  OutputStream  InputStream extract (i.e reads) data from the source (file) and sends it to the program.  OutputStream takes data from the program and sends(i.e writes) it to the destination (file).  Lecture/core/io/23 1  Stream is often equipped with a buffer in memory.  A buffer is simply a block of memory that is used to batch up the data that is transferred to from an external device. feel the Technology…
  2. 2. Core Java Debasish Pratihari Stream Classes The java.io package contains a large number of stream classes that provides capabilities for processing all types of data. These classes may be organized into two groups depending upon the data type they operate.  Byte Stream Classes  Character Stream Classes Byte Stream Classes Byte Stream Classes have been designed to provide functional features for creating and manipulating stream and files for reading and writing bytes. Since the streams are unidirectional, they can transmit bytes in only one direction and therefore java provides two kinds of byte stream classes : InputStream and OutputStream classes. InputStream Classes Input stream classes that are used to read 8-bit (I byte) include a super class know as InputStream and number of sub-classes for supporting various input-related functions. Program Architecture of File Copy Program ins Stream Input.txt read( ) inFile Program Output.txt outFile Lecture/core/io/23 write( ) outs Stream 2 feel the Technology…
  3. 3. Core Java Debasish Pratihari Sample Program-1 Program Objective : To Copy Characters from one File to another. File Name : CopyChars.java import java.io.*; class CopyChars{ public static void main(String args[]){ File inFile = new File("Input.txt"); File outFile = new File("Output.txt"); FileReader ins= null; FileWriter outs=null; try{ ins= new FileReader(inFile); outs=new FileWriter(outFile); int ch; while((ch=ins.read())!= -1) outs.write(ch); }catch(IOException e){ System.out.println(e); System.exit(0); } finally{ try{ ins.close(); outs.close(); }catch(IOException e){ System.out.println(e); } } } } Lecture/core/io/23 3 feel the Technology…
  4. 4. Core Java Debasish Pratihari Programming Architecture to Deal with Primitive Data type : Bytes are read from the file Bytes are converted to primitive types fis Primitive Types are read from dis dis prim.txt Program Screen primitive fos Bytes are written to the file dos Primitives are converted to a sequence of bytes Primitive Types are written to dos Sample Prohram-2 25% Program Objective : To deal with primitive Data types File Name : PrimitiveDemo.java import java.io.*; class PrimitiveDemo{ public static void main(String args[]) throws IOException{ File primitive = new File("prim.txt"); FileOutputStream fos = new FileOutputStream(primitive); DataOutputStream dos=new DataOutputStream(fos); dos.writeInt(1234); dos.writeDouble(34.45); dos.writeBoolean(false); dos.writeChar('a'); dos.close(); fos.close(); FileInputStream fis=new FileInputStream(primitive); DataInputStream dis=new DataInputStream(fis); System.out.println(dis.readInt()); System.out.println(dis.readDouble()); System.out.println(dis.readBoolean()); System.out.println(dis.readChar()); dis.close(); fis.close(); } } Lecture/core/io/23 4 feel the Technology…