1. File Handling Basics

File handling means reading data from files and writing data to files.

Java mainly provides file-handling classes through packages like:

java.io
java.nio

For basic interview knowledge, focus on the java.io classes below.

2. InputStream

InputStream is used to read byte-based data.

Useful for:

• Images
• PDFs
• Binary files
• Other raw byte data

Example:

InputStream in = new FileInputStream("data.txt");

3. OutputStream

OutputStream is used to write byte-based data.

Example:

OutputStream out = new FileOutputStream("data.txt");