Java File I/O – Read and Write Files
📄 Java File I/O – Read and Write Files
Java provides powerful and flexible APIs for file input and output (I/O), allowing you to read from and write to files easily. File I/O in Java can be done using several classes from the java.io and java.nio.file packages.
✅ 1. Reading Files in Java
🔹 Using BufferedReader
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import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class ReadFileExample {
public static void main(String[] args) {
try (BufferedReader reader = new BufferedReader(new FileReader("example.txt"))) {
String line;
while ((line = reader.readLine()) != null) {
System.out.println(line);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
🔹 Using Files.readAllLines (Java 8+)
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import java.nio.file.Files;
import java.nio.file.Paths;
import java.io.IOException;
import java.util.List;
public class ReadFileWithNIO {
public static void main(String[] args) {
try {
List<String> lines = Files.readAllLines(Paths.get("example.txt"));
lines.forEach(System.out::println);
} catch (IOException e) {
e.printStackTrace();
}
}
}
✅ 2. Writing to Files in Java
🔹 Using BufferedWriter
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import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
public class WriteFileExample {
public static void main(String[] args) {
try (BufferedWriter writer = new BufferedWriter(new FileWriter("output.txt"))) {
writer.write("Hello, Java File I/O!");
writer.newLine();
writer.write("This is a second line.");
} catch (IOException e) {
e.printStackTrace();
}
}
}
🔹 Using Files.write (Java 8+)
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import java.nio.file.Files;
import java.nio.file.Paths;
import java.io.IOException;
import java.util.Arrays;
public class WriteFileWithNIO {
public static void main(String[] args) {
try {
Files.write(Paths.get("output.txt"), Arrays.asList("Line 1", "Line 2"));
} catch (IOException e) {
e.printStackTrace();
}
}
}
🧠 Tips for File I/O in Java
Always close resources or use try-with-resources to prevent memory leaks.
Handle IOExceptions gracefully.
Use Paths.get("filename") instead of hard-coded paths for portability.
Prefer java.nio.file package for modern file operations (Java 7+).
🧪 Bonus: Append to a File
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try (BufferedWriter writer = new BufferedWriter(new FileWriter("output.txt", true))) {
writer.write("This line will be appended.");
writer.newLine();
} catch (IOException e) {
e.printStackTrace();
}
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