Notes on core java

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.
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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
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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
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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
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