Welcome to another lesson, where we'll delve into the essential technique of reading files line-by-line using Java's Files and Paths classes. In many practical applications, especially those involving large files such as logs or continuous data streams, processing data one line at a time is crucial for efficient data management. By the end of this lesson, you'll learn how to effectively read and process file data line-by-line using Java.

To read a file line-by-line in Java, you can use the Files.readAllLines method to read the lines into a List<String>, and then iterate over the list using a for-each loop. Let's see this in action:

Here, Files.readAllLines(filePath) reads lines from data.txt and stores them in a list. Each line is then printed to the console.

Imagine needing to process a set of numbers stored in a file — reading each integer and calculating their sum. This is a practical task you can easily accomplish using Files.readAllLines and basic string manipulation in Java.

Assume numbers.txt contains:

The following code reads integers from this file and calculates their sum:

• Reading Numbers: Each line is parsed to an integer using Integer.parseInt(), which safely converts strings to integers.
• Calculating Sum: The integers are added together in the totalSum variable.

After running this code, it will display the total sum of the numbers:

In this lesson, you've developed the skills to read a text file line-by-line using Java — a crucial technique for processing large datasets efficiently. You've learned to manage file I/O operations with Files and Paths, and effectively handle each line of text data. You're now well-prepared to tackle practice exercises applying these concepts and further explore parsing techniques in upcoming lessons. Continue building on these skills and enjoy the journey!