Java Programming
📁 Java File Handling (Important ⭐)
File Handling allows Java programs to create, read, write, update, and delete files.
It is useful when your application needs to work with data stored outside the program.
Examples:
• 📄 Reading a text file
• 📝 Writing data to a file
• 📊 Processing CSV files
• 📋 Creating reports
• 💾 Storing application data
✅ 1️⃣ What is File Handling?
File Handling means performing operations on files using Java.
Common operations:
Create
Read
Write
Append
Delete
Java provides several classes for this purpose.
🔹 2️⃣ Important File Handling Classes
Some commonly used classes are:
File
FileReader
FileWriter
BufferedReader
BufferedWriter
Each has a different purpose.
🔹 3️⃣ File Class
The "File" class is used to work with file and directory information.
Example:
import java.io.File;
class FileDemo {
public static void main(String[] args) {
File file = new File("data.txt");
System.out.println(file.exists());
}
}
If "data.txt" exists:
true
Otherwise:
false
🔹 4️⃣ Creating a File
You can create a new file using "createNewFile()".
import java.io.File;
import java.io.IOException;
class CreateFile {
public static void main(String[] args) throws IOException {
File file = new File("data.txt");
if (file.createNewFile()) {
System.out.println("File created");
} else {
System.out.println("File already exists");
}
}
}
🔹 5️⃣ Writing to a File
"FileWriter" can be used to write text into a file.
import java.io.FileWriter;
import java.io.IOException;
class WriteFile {
public static void main(String[] args) throws IOException {
FileWriter writer = new FileWriter("data.txt");
writer.write("Welcome to Java");
writer.close();
}
}
The file will contain:
Welcome to Java
🔹 6️⃣ Appending Data
By default, "FileWriter" can overwrite existing content.
To append instead:
FileWriter writer = new FileWriter("data.txt", true);
writer.write("\nLearning File Handling");
writer.close();
Now the file contains:
Welcome to Java
Learning File Handling
🔹 7️⃣ Reading a File
"FileReader" can read characters from a file.
import java.io.FileReader;
import java.io.IOException;
class ReadFile {
public static void main(String[] args) throws IOException {
FileReader reader = new FileReader("data.txt");
int character;
while ((character = reader.read()) != -1) {
System.out.print((char) character);
}
reader.close();
}
}
Output:
Welcome to Java
Learning File Handling
⭐ 8️⃣ BufferedReader
"BufferedReader" is useful for reading text efficiently, especially line by line.
Example:
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
class ReadFile {
public static void main(String[] args) throws IOException {
BufferedReader reader =
new BufferedReader(new FileReader("data.txt"));
String line;
while ((line = reader.readLine()) != null) {
System.out.println(line);
}
reader.close();
}
}
👉 "readLine()" reads one complete line at a time.
🔹 9️⃣ BufferedWriter
"BufferedWriter" can efficiently write text to a file.
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