FileReader and FileWriter Class in Java
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Introduction to FileReader and FileWriter Classes in Java
The FileReader and FileWriter classes in Java are used for reading and writing text files, respectively. They are both character-oriented classes, which means that they read and write data one character at a time.
FileReader is used to read data from a text file, one character at a time.To create a FileReader object, you must pass the path to the file you want to read as a constructor argument.
FileWriter is used to write data to a text file, one character at a time. It can be used to write any type of text file, including text documents, HTML files, and XML files. To create a FileWriter object, you must pass the path to the file you want to write to as a constructor argument.
FileReader and FileWriter are very powerful classes for reading and writing text files in Java. They are used in a wide variety of applications, including text editors, web browsers, and database applications.
Here are some additional things to keep in mind when using FileReader and FileWriter:
- Both FileReader and FileWriter are subclasses of the Reader and Writer classes, respectively. This means that they inherit all of the methods from these parent classes.
- FileReader and FileWriter are both AutoCloseable classes. This means that they can be automatically closed using the try-with-resources statement.
- If you are writing to a file that does not exist, FileWriter will create the file for you.
- If you are writing to a file that already exists, FileWriter will overwrite the contents of the file.
- To append data to an existing file, you can use the FileWriter constructor that takes a boolean parameter. If you set this parameter to true, FileWriter will append data to the end of the file instead of overwriting it.
Methods of FileReader Class
| Method | Description |
|---|---|
| close() | Closes the FileReader object. |
| mark() | Marks the current position in the FileReader object. |
| markSupported() | Returns true if the FileReader object supports marking. |
| read() | Reads a single character from the FileReader object. |
| read(char[] cbuf) | Reads an array of characters from the FileReader object. |
| read(char[] cbuf, int off, int len) | Reads an array of characters from the FileReader object, starting at the specified offset and reading the specified number of characters. |
| reset() | Resets the FileReader object to the last marked position. |
| skip() | Skips n characters in the FileReader object. |
Methods of FileWriter Class
| Method | Description |
|---|---|
| close() | Closes the FileWriter object. |
| flush() | Flushes the data in the FileWriter object to the underlying file. |
| write(int c) | Writes a single character to the FileWriter object. |
| write(char[] cbuf) | Writes an array of characters to the FileWriter object. |
| write(char[] cbuf, int off, int len) | Writes an array of characters to the FileWriter object, starting at the specified offset and writing the specified number of characters. |
| write(String str) | Writes a string to the FileWriter object. |
| write(String str, int off, int len) | Writes a portion of a string to the FileWriter object, starting at the specified offset and writing the specified number of characters. |
Exercises
Write a program to read a Character from a file using FileReader Class in Java
package javaprogrammingdemo;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.util.*;
public class javalabclass{
public static void main(String args[]) {
//Reading a Character from a file
try
{
//filereader - read characters
FileReader fr = new FileReader("satish.txt");
int data=fr.read();
System.out.println((char)data);
fr.close();
}
catch(IOException e)
{
System.out.println("check file");
}
catch(Exception e)
{
System.out.println("Exception caught here");
}
}
} Write a program to read an Array of Characters from a File using FileReader Class in Java
package practiceproject;
import java.io.*;
import java.util.*;
public class democlass {
public static void main(String[] args) throws IOException {
File obj = new File("satish.txt");
FileReader fin = new FileReader(obj);
char c[]=new char[4];
fin.read(c);
for(char k:c)
{
System.out.println(k);
}
}
} Write a program to read characters into an array from a file using offset using FileReader Class in Java
package practiceproject;
import java.io.*;
import java.util.*;
public class democlass {
public static void main(String[] args) throws IOException {
File obj = new File("satish.txt");
FileReader fin = new FileReader(obj);
char c[]=new char[4];
fin.read(c,1,2);
for(char k:c)
{
System.out.println(k);
}
}
} Write a Java Program to write a character to a file using FileWriter Class in Java
package practiceproject;
import java.io.*;
import java.util.*;
public class democlass {
public static void main(String[] args) throws IOException {
File obj = new File("satish.txt");
FileWriter fout = new FileWriter(obj);
if(obj.canWrite())
{
fout.write('S');
}
fout.close();
}
} Write a Java Program write an array of characters to a file using FileWriter Class
package practiceproject;
import java.io.*;
import java.util.*;
public class democlass {
public static void main(String[] args) throws IOException {
File obj = new File("satish.txt");
FileWriter fout = new FileWriter(obj);
char c[]= {'s','a','t','i','s','h'};
if(obj.canWrite())
{
fout.write(c);
}
fout.close();
}
} Write a Java Program to write a String to a file using FileWriter Class
package practiceproject;
import java.io.*;
import java.util.*;
public class democlass {
public static void main(String[] args) throws IOException {
File obj = new File("satish.txt");
FileWriter fout = new FileWriter(obj);
String s = "satish is writing here";
if(obj.canWrite())
{
fout.write(s);
}
fout.close();
}
} Write a Java Program to append data to a file using FileWriter Class
package practiceproject;
import java.io.*;
import java.util.*;
public class democlass {
public static void main(String[] args) throws IOException {
File obj = new File("output8.txt");
FileWriter fout = new FileWriter(obj,true);
try
{
String str="new message here";
fout.write(str);
System.out.println("file writing successful");
}
catch(Exception e)
{
System.out.println(e.getMessage());
}
finally
{
fout.close();
}
}
}