Reading files is a fundamental part of file handling in Java. It involves opening a file, reading its contents, and then processing or displaying the data. Java provides several classes in the java.io and java.nio packages to handle file reading. In this lesson, we focus on the traditional I/O approach using classes like FileReader and BufferedReader to read text files.

Key Concepts in Reading Files

Below is a table that summarizes key concepts and classes used in reading files:

Steps for Reading a File

1. Open the File: Create a FileReader object that points to the file you want to read.
2. Wrap the Reader: Wrap the FileReader in a BufferedReader to read lines efficiently.
3. Read the File Content: Use the readLine() method in a loop to read the file line by line.
4. Handle Exceptions: File operations can throw an IOException, so proper exception handling is necessary.
5. Close the File: Use try-with-resources to automatically close the file when done.

Examples

Example 1: Reading a File Line by Line

In this example, we demonstrate how to read a text file named "input.txt" line by line using BufferedReader and try-with-resources. The code will display each line in the console.

Example Explanation:

• Opening the File:
  A FileReader is created for "input.txt" and wrapped inside a BufferedReader to improve efficiency.
• Reading Lines:
  The readLine() method reads each line until it returns null, indicating the end of the file.
• Error Handling:
  A try-catch block is used to handle any IOException that may occur during file reading.
• Resource Management:
  Try-with-resources automatically closes the BufferedReader when the block is exited.

Example 2: Using Scanner to Read a File

In this example, we use the Scanner class to read the contents of "input.txt" line by line. The code prints each line to the console.

Example Explanation:

• File Object Creation:
  A File object is instantiated to represent "input.txt".
• Reading with Scanner:
  A Scanner is used to read the file, with hasNextLine() and nextLine() iterating through each line.
• Exception Handling:
  The try-with-resources statement ensures the Scanner is closed, and a catch block handles the FileNotFoundException.

Reading files in Java is accomplished by using classes such as FileReader, BufferedReader, and Scanner. These classes allow you to open a file, read its content line by line, and handle any potential I/O errors gracefully. The examples provided demonstrate two common approaches: