Java Read Files

📖 Java Read Files

Java provides several ways to read data from files, mainly using:

File + Scanner
FileReader
BufferedReader
Files.readAllLines() (Java NIO)
FileInputStream (for binary data)

1. Reading a File Using `Scanner`

import java.io.File;
import java.util.Scanner;

public class ReadFileScanner {
public static void main(String[] args) {
try {
File file = new File("example.txt");
Scanner sc = new Scanner(file);

while (sc.hasNextLine()) {
System.out.println(sc.nextLine());
}
sc.close();
} catch (Exception e) {
System.out.println("Error: File not found!");
}
}
}

import java.io.File;

import java.util.Scanner;

public class ReadFileScanner {

public static void main(String[] args) {

try {

File file = new File("example.txt");

Scanner sc = new Scanner(file);

while (sc.hasNextLine()) {

System.out.println(sc.nextLine());

}

sc.close();

} catch (Exception e) {

System.out.println("Error: File not found!");

}

Simple and effective for small text files.
hasNextLine() checks if the file has more lines.

2. Reading a File Using `FileReader`

import java.io.FileReader;
import java.io.IOException;

public class ReadFileReader {
public static void main(String[] args) {
try {
FileReader reader = new FileReader("example.txt");
int i;
while ((i = reader.read()) != -1) { // reads character by character
System.out.print((char)i);
}
reader.close();
} catch (IOException e) {
System.out.println("Error reading file!");
}
}
}

import java.io.FileReader;

import java.io.IOException;

public class ReadFileReader {

public static void main(String[] args) {

try {

FileReader reader = new FileReader("example.txt");

int i;

while ((i = reader.read()) != -1) { // reads character by character

System.out.print((char)i);

}

reader.close();

} catch (IOException e) {

System.out.println("Error reading file!");

}

Reads character by character.
Good for simple text processing.

3. Reading a File Using `BufferedReader` (Recommended)

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class ReadFileBuffered {
public static void main(String[] args) {
try (BufferedReader br = new BufferedReader(new FileReader("example.txt"))) {
String line;
while ((line = br.readLine()) != null) { // reads line by line
System.out.println(line);
}
} catch (IOException e) {
System.out.println("Error reading file!");
}
}
}

import java.io.BufferedReader;

import java.io.FileReader;

import java.io.IOException;

public class ReadFileBuffered {

public static void main(String[] args) {

try (BufferedReader br = new BufferedReader(new FileReader("example.txt"))) {

String line;

while ((line = br.readLine()) != null) { // reads line by line

System.out.println(line);

}

} catch (IOException e) {

System.out.println("Error reading file!");

}

More efficient for large files.
Reads line by line instead of character by character.

4. Reading a File Using `Files.readAllLines()` (Java NIO)

import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;

public class ReadFileNIO {
public static void main(String[] args) {
try {
List<String> lines = Files.readAllLines(Paths.get("example.txt"));
for (String line : lines) {
System.out.println(line);
}
} catch (Exception e) {
System.out.println("Error reading file!");
}
}
}

import java.nio.file.Files;

import java.nio.file.Paths;

import java.util.List;

public class ReadFileNIO {

public static void main(String[] args) {

try {

List<String> lines = Files.readAllLines(Paths.get("example.txt"));

for (String line : lines) {

System.out.println(line);

}

} catch (Exception e) {

System.out.println("Error reading file!");

}

Modern and concise approach.
Returns a List of lines.

5. Reading Binary Files Using `FileInputStream`

import java.io.FileInputStream;
import java.io.IOException;

public class ReadBinaryFile {
public static void main(String[] args) {
try (FileInputStream fis = new FileInputStream("binary.dat")) {
int i;
while ((i = fis.read()) != -1) { // reads byte by byte
System.out.print((char)i);
}
} catch (IOException e) {
System.out.println("Error reading binary file!");
}
}
}

import java.io.FileInputStream;

import java.io.IOException;

public class ReadBinaryFile {

public static void main(String[] args) {

try (FileInputStream fis = new FileInputStream("binary.dat")) {

int i;

while ((i = fis.read()) != -1) { // reads byte by byte

System.out.print((char)i);

}

} catch (IOException e) {

System.out.println("Error reading binary file!");

}

Useful for reading images, audio, and other binary files.

🧠 Summary Table

Method	Use Case
`Scanner`	Small text files, easy to use
`FileReader`	Simple character-by-character reading
`BufferedReader`	Efficient for large text files, line-by-line reading
`Files.readAllLines()`	Modern, concise, easy for small to medium files
`FileInputStream`	Binary files (images, audio, etc.)

Best Practice

Always close resources or use try-with-resources:

Java Read Files

📖 Java Read Files

1. Reading a File Using Scanner

2. Reading a File Using FileReader

3. Reading a File Using BufferedReader (Recommended)

4. Reading a File Using Files.readAllLines() (Java NIO)

5. Reading Binary Files Using FileInputStream

🧠 Summary Table

Best Practice

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1. Reading a File Using `Scanner`

2. Reading a File Using `FileReader`

3. Reading a File Using `BufferedReader` (Recommended)

4. Reading a File Using `Files.readAllLines()` (Java NIO)

5. Reading Binary Files Using `FileInputStream`