Java I/O Streams

💻 Java I/O Streams

In Java, I/O (Input/Output) Streams are used to read data from a source or write data to a destination.

InputStream → Read data (input)
OutputStream → Write data (output)

Streams handle byte-level or character-level data.

🧩 Types of Streams

1️⃣ Based on Data Type

Stream Type	Description
Byte Streams	Read/write binary data (images, files, audio)
Character Streams	Read/write text data (characters, strings)

2️⃣ Based on Direction

Direction	Class/Interface
Input	`InputStream`, `Reader`
Output	`OutputStream`, `Writer`

✅ 1. Byte Streams (Binary Data)

InputStream → Read bytes
OutputStream → Write bytes

Example: Reading a File Using `FileInputStream`

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

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

import java.io.FileInputStream;

import java.io.IOException;

public class ByteInputExample {

public static void main(String[] args) {

try (FileInputStream fis = new FileInputStream("example.txt")) {

int i;

while ((i = fis.read()) != -1) {

System.out.print((char) i); // convert byte to char

}

} catch (IOException e) {

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

}

Example: Writing a File Using `FileOutputStream`

import java.io.FileOutputStream;
import java.io.IOException;

public class ByteOutputExample {
public static void main(String[] args) {
try (FileOutputStream fos = new FileOutputStream("output.txt")) {
String data = "Hello using FileOutputStream!";
fos.write(data.getBytes()); // convert string to bytes
} catch (IOException e) {
System.out.println("Error writing file.");
}
}
}

import java.io.FileOutputStream;

import java.io.IOException;

public class ByteOutputExample {

public static void main(String[] args) {

try (FileOutputStream fos = new FileOutputStream("output.txt")) {

String data = "Hello using FileOutputStream!";

fos.write(data.getBytes()); // convert string to bytes

} catch (IOException e) {

System.out.println("Error writing file.");

}

✅ 2. Character Streams (Text Data)

Reader → Read characters
Writer → Write characters

Example: Reading Using `FileReader`

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

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

import java.io.FileReader;

import java.io.IOException;

public class CharReadExample {

public static void main(String[] args) {

try (FileReader fr = new FileReader("example.txt")) {

int i;

while ((i = fr.read()) != -1) {

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

}

} catch (IOException e) {

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

}

Example: Writing Using `FileWriter`

import java.io.FileWriter;
import java.io.IOException;

public class CharWriteExample {
public static void main(String[] args) {
try (FileWriter fw = new FileWriter("output.txt")) {
fw.write("Hello Java FileWriter!");
} catch (IOException e) {
System.out.println("Error writing file.");
}
}
}

import java.io.FileWriter;

import java.io.IOException;

public class CharWriteExample {

public static void main(String[] args) {

try (FileWriter fw = new FileWriter("output.txt")) {

fw.write("Hello Java FileWriter!");

} catch (IOException e) {

System.out.println("Error writing file.");

}

✅ 3. Buffered Streams (Efficient I/O)

Wrap streams to buffer data → improves performance
Classes: BufferedReader, BufferedWriter, BufferedInputStream, BufferedOutputStream

Example: BufferedReader

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

public class BufferedReaderExample {
public static void main(String[] args) {
try (BufferedReader br = new BufferedReader(new FileReader("example.txt"))) {
String line;
while ((line = br.readLine()) != null) {
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 BufferedReaderExample {

public static void main(String[] args) {

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

String line;

while ((line = br.readLine()) != null) {

System.out.println(line);

}

} catch (IOException e) {

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

}

✅ 4. Data Streams (Read/Write Primitive Data)

DataInputStream → Read primitive types (int, double, etc.)
DataOutputStream → Write primitive types

import java.io.DataOutputStream;
import java.io.FileOutputStream;

public class DataStreamExample {
public static void main(String[] args) {
try (DataOutputStream dos = new DataOutputStream(new FileOutputStream("data.dat"))) {
dos.writeInt(100);
dos.writeDouble(99.99);
} catch (Exception e) {
System.out.println("Error writing data stream.");
}
}
}

import java.io.DataOutputStream;

import java.io.FileOutputStream;

public class DataStreamExample {

public static void main(String[] args) {

try (DataOutputStream dos = new DataOutputStream(new FileOutputStream("data.dat"))) {

dos.writeInt(100);

dos.writeDouble(99.99);

} catch (Exception e) {

System.out.println("Error writing data stream.");

}

🧠 Summary Table

Stream Type	Class Example	Use Case
Byte Input	`FileInputStream`	Read binary files
Byte Output	`FileOutputStream`	Write binary files
Character Input	`FileReader`	Read text files
Character Output	`FileWriter`	Write text files
Buffered	`BufferedReader`/`BufferedWriter`	Efficient text I/O
Data Streams	`DataInputStream`/`DataOutputStream`	Read/write primitives

Best Practices

Always close streams (use try-with-resources).
Use Buffered streams for better performance with large files.
Choose byte streams for binary data and character streams for text.

Java I/O Streams

💻 Java I/O Streams

🧩 Types of Streams

1️⃣ Based on Data Type

2️⃣ Based on Direction

✅ 1. Byte Streams (Binary Data)

Example: Reading a File Using FileInputStream

Example: Writing a File Using FileOutputStream

✅ 2. Character Streams (Text Data)

Example: Reading Using FileReader

Example: Writing Using FileWriter

✅ 3. Buffered Streams (Efficient I/O)

Example: BufferedReader

✅ 4. Data Streams (Read/Write Primitive Data)

🧠 Summary Table

Best Practices

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Example: Reading a File Using `FileInputStream`

Example: Writing a File Using `FileOutputStream`

Example: Reading Using `FileReader`

Example: Writing Using `FileWriter`