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SUBJECT: COMPUTER APPLICATIONS
TOPIC: FILE HANDLING
Name:
Grade :11 ISC Prepared by : Ms. CHANDNI MATHUR
Reader, InputStreamReader, FileReader and BufferedReader
Reader is the abstract class for reading character streams. It implements the following
fundamental methods:
read(): reads a single character.
read(char[]): reads an array of characters.
skip(long): skips some characters.
close(): closes the stream.
InputStreamReader is a bridge from byte streams to character streams. It converts bytes
into characters using a specified charset. The charset can be default character encoding of the
operating system, or can be specified explicitly when creating an InputStreamReader.
FileReader is a convenient class for reading text files using the default character encoding of
the operating system.
BufferedReader reads text from a character stream with efficiency (characters are buffered
to avoid frequently reading from the underlying stream) and provides a convenient method
for reading a line of text readLine().
The following diagram show relationship of these reader classes in the java.io package:
2. Writer, OutputStreamWriter, FileWriter and BufferedWriter
Writer is the abstract class for writing character streams. It implements the following
fundamental methods:
write(int): writes a single character.
write(char[]): writes an array of characters.
write(String): writes a string.
close(): closes the stream.
OutputStreamWriter is a bridge from byte streams to character streams. Characters are
encoded into bytes using a specified charset. The charset can be default character encoding of
the operating system, or can be specified explicitly when creating an OutputStreamWriter.
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FileWriter is a convenient class for writing text files using the default character encoding of
the operating system.
BufferedWriter writes text to a character stream with efficiency (characters, arrays and
strings are buffered to avoid frequently writing to the underlying stream) and provides a
convenient method for writing a line separator: newLine().
The following diagram show relationship of these writer classes in the java.io package:
// Java Program to illustrate reading fromFileReader using FileReader
import java.io.*;
public class ReadingFromFile
{
public static void main(String[] args) throws Exception
{
try {
FileReader reader =new FileReader("C:\\Users\\COM310\\Desktop\\test1.txt");
int character;
while ((character = reader.read()) != -1) {
System.out.print((char) character);
}
reader.close();
} catch (IOException e) {
}
}
}
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// Java Program to illustrate reading from FileWriter using FileWriter
import java.io.*;
public class WritingToFile {
public static void main(String[] args) {
try {
FileWriter writer = new FileWriter("C:\\Users\\COM310\\Desktop\\test.txt", true);
writer.write("Hello World");
writer.write("\n"); // write new line
writer.write("Good Bye!");
writer.close();
} catch (IOException e) {
//e.printStackTrace();
}
}
// Java Program to illustrate write fruits name in text file(fruits.txt)
import java.io.*;
class FileWrite
{
public static void main(String args[])throws IOException
{
FileWriter fw = new FileWriter("C:\\Users\\Chandni\\Desktop\\fruits.txt", true);
BufferedWriter bw = new BufferedWriter(fw);
PrintWriter pw= new PrintWriter(bw);
pw.println("Apple");
pw.println("Grapes");
pw.println("kiwi");
pw.println("orange");
pw.close();
}
}
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// Java Program to illustrate read contents already present from fruits.txt
import java.io.*;
class FileRead
{
public static void main(String args[])throws IOException
{
FileReader fr = new FileReader("C:\\Users\\Chandni\\Desktop\\fruits.txt");
BufferedReader br = new BufferedReader(fr);
String n;
while((n=br.readLine())!=null)
{
System.out.println(n);
}
}
}
//Java program to write your name and marks into a binary or data file(abc.dat)
import java.io.*;
class DataFileWrite
{
public static void main(String args[])throws IOException
{
FileOutputStream fos = new FileOutputStream("C:\\Users\\Chandni\\Desktop\\abc.dat");
DataOutputStream dos= new DataOutputStream(fos);
dos.writeUTF("Ajay");
dos.writeInt(5);
}
}
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//Java program to read from the data file (abc.dat)
import java.io.*;
class ReadData
{
public static void main(String args[])throws IOException
{
FileInputStream fis = new FileInputStream("C:\\Users\\Chandni\\Desktop\\abc.dat");
DataInputStream dis= new DataInputStream(fis);
boolean eof= false;
while(!eof)
{
try
{
String n= dis.readUTF();
int m= dis.readInt();
System.out.println("name= "+ n + "\n Marks= " + m);
}
catch(EOFException e)
{
eof=true;
}
}
}
}
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Question:
A binary file named “ABC.DAT” contains the product code (pc), unit price (up) and
quantity(q) for number of items.
Write a Method to accept a product code ‘p’ and check the availability of the product
and display with an appropriate message.
The method declaration is as follows:
void findpro( int p )
Solution:
void findPro(int p) throws IOException)
{
FileInputStream fis = new FileInputStream("C:\\Users\\Chandni\\Desktop\\abc.dat");
DataInputStream dis= new DataInputStream(fis);
boolean eof= false;
int flag=0;
while(!eof)
{
try
{
int pc= dis.readInt();
int up= dis.readInt();
int q= dis.readInt();
if (p==pc)
{
System.out.println(“Product Found”);
System.out.println(“product Code =” + pc);
System.out.println(“Unit Price =” + up);
System.out.println(“Quantity =” + q);
flag=1;
}
}
catch(EOFException e)
{
eof=true;
}
if( flag==0)
System.out.println(“Product Not Found”);
}
dis.close();
fis.close();
}
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