Session 8 : Java IO
Java
IO
Q?
What is Stream
/>
all the I/O operations in
java depends on the abstraction of stream( flow of data)
/>
this flow of data can come from : file
in the disk – standard
input/output – network
connection- whatever hw
devices
/>
this I/O operations works in the same way for all
the kinds of stream
/>
library classes are in package : java.io
/>
the exception are the subclasses of IOException
Q?
how do we read the character (InputStream)
/>
int
read();
method
/>
reads the single character and returns -1 if End Of Stream occurs
/>
to read a line we can use this read() method in the loop
Q?
how do we write the character (OutputStream)
/>
int
write();
method
/>
write the char in output stream
Q?
how do we use BufferedReader to read a file from the stream;
/> we
use the BufferedReader Class : this class provides the method for
efficient reading of char, arrays,
and lines.
/>
the best part is that it uses a default-sized
input buffer to start buffering the char-input stream
/>
FileReader is the class used
for reading char files
/>
readLine() method reads a
single line of text excluding the termination character, or null if
an end of the stream has been reached
/>
here I have also discussed the implementation
of using IOException to handle error in case of file reading
BufferedReader
reader = null;
try
{
File
file
= new
File("fileName.txt");
reader
= new
BufferedReader(new
FileReader(file));
String line;
while
((line
= reader.readLine())
!= null)
{
System.out.println(line);
}
}
catch
(IOException
e)
{
e.printStackTrace();
}
finally
{
try
{
reader.close();
} catch
(IOException
e) {
e.printStackTrace();
}
}
Q?
what Java File class consits of
/>
static
methods that operate on files, directories, or other types of
files.
/>Java
File class represents the files and
directory pathnames in an abstract manner.
/>This
class is used for creation of files and directories, file searching,
file deletion etc.
Q?
what is StringTokenizer
/>
The StringTokenizer class provides
the first step in this parsing
process. So given the input string, you can enumerate the
individual tokens contained in it.
/>
this works on Stream of data
/>
to use this class we have to
specify an input string and
a string that contains delimiters.
Delimiters are characters that separate
tokens.
/>
set of delimiters are (blank,
“,”,\t,\n,\r,\f) : blank is the default delimiter
/>
import
java.util.StringTokenizer;
class
STDemo {
static
String in
= "title=Jumping-Fox;"
+
"author=Niranjan
K;"
+
"publisher=niranjanandkhatri.blogspot.it;"
+
"funnyAct
2014;";
public
static
void
main(String args[])
{
StringTokenizer
st
= new
StringTokenizer(in,
"=;");
while(st.hasMoreTokens())
{
String
key
= st.nextToken();
String
val
= st.nextToken();
System.out.println(key
+ "\t"
+ val);
}
}
}
Output:
title
Jumping-Fox
author Niranjan
K
publisher niranjanandkhatri.blogspot.it
funnyAct
2014
Q?
what is serialization in java
/>mechanism,
where an object can be represented as a sequence of bytes that
includes the object's data as well as information about the object's
type and the types of data stored in the object.
To
perfom serialization two things must be done :
/>
must implement the java.io.Serializable
interface.
/>
All of the fields in the class must
be serializable. If a field is not serializable, it must be
marked transient.
Ex:
public
class
Employee
implements
java.io.Serializable
{
public
String name;
public
String address;
public
transient
int
SSN;
public
int
number;
public
void
mailCheck()
{
System.out.println("Mailing
a check to "
+ name
+ "
"
+ address);
}
}
import
java.io.*;
public
class
SerializeDemo
{
public
static
void
main(String [] args)
{
Employee
e = new
Employee();
e.name = "Niranjan
Khatri";
e.address = "Turin,
Italy";
e.SSN = 11122333;
e.number = 101;
try
{
FileOutputStream fileOut =
new
FileOutputStream("/tmp/employee.ser");
ObjectOutputStream out = new
ObjectOutputStream(fileOut);
out.writeObject(e);
out.close();
fileOut.close();
System.out.printf("Serialized
data is saved in /tmp/employee.ser");
}catch(IOException
i)
{
i.printStackTrace();
}
}
}
System.out.println(key
+ "\t"
+ val);
}
}
}
Comments
Post a Comment