Java makes available a set of classes and methods that allows you to read from and write to files. Java supports both streams and methods to read from and write to file respectively.
Example: Read file using FilelnputStream
import java.io.*;
class ShowFile
{
public static void main(String ar[]) throws IOException
{
int ch;
FileInputStream finObj;
try
{
finObj = new FileInputStream(“ShowFile.java”);
}
catch(FileNotFoundException e)
{
System.out.println(“File Not Found”);
return;
}
do
{
ch = finObj.read();
if(ch != -1)
System.out.print((char) ch);
} while(ch != -1);
finObj.close();
}
}
Output
Print contents of own source file, read character by character and write character by character.
Example: Read file using FileReader
import java.io.*;
class FileRead
{
public static void main(String arg[]) throws IOException
{
FileReader frObj = new FileReader(“FileRead.java”);
BufferedReader brObj = new BufferedReader(frObj);
String str;
while ((str = brObj.readLine ())!=null)
System.out.println(str);
frObj.close();
}
}
Output
Read the file content line by line, and print in the same manner.
Example: Writing data using FileOutputStream
import java.io.*;
class CopyFile
{
public static void main(String arg[]) throws IOException
{
int i;
FileInputStream finObj;
FileOutputStream foutObj;
try
{
try
{
finObj = new FileInputStream(arg[0]);
}
catch(FileNotFoundException e)
{
System.out.println(“File ” + arg[0] + ” not Found”);
return;
}
try
{
foutObj = new FileOutputStream(arg[1]);
}
catch(FileNotFoundException e)
{
System.out.println(“File” +arg[1]+” not found”);
return;
}
}
catch(ArrayIndexOutOfBoundsException e)
{
System.out.println(“Argument missing”);
return;
}
try
{
do
{
i = finObj.read();
if(i != -1)
foutObj.write(i);
}while(i != -1);
}
catch(IOException e)
{
System.out.println(“Some file error occurd”);
}
finObj.close();
foutObj.close();
}
}
Output:
Copy content of a.txt to b.txt
It is clear form the output window given above that content of a.txt has been copied to b.txt.
Example: Writing data using FileWriter
import java.io.*;
public class WriteFile
{
public static void main(String[] args) throws IOException
{
File inputFileObj = new File(“a.txt”);
File outputFileObj = new File(“b.txt”);
FileReader finObj = new FileReader(inputFileObj);
FileWriter foutObj = new FileWriter(outputFileObj);
int c;
while ((c = finObj.read()) != -1)
foutObj.write(c);
finObj.close();
foutObj.close();
}
}
Output:
Copy content of a.txt to b.txt
Dinesh Thakur holds an B.C.A, MCDBA, MCSD certifications. Dinesh authors the hugely popular