Welcome to the first lesson of our course on "Parsing Table Data in Java". In this lesson, we will explore reading and processing table-like data from a text file using Java. This skill is crucial for tasks involving data analysis, generating reports, and various applications requiring structured data manipulation in software development. By the end of this lesson, you'll understand how to parse a 2D table from a file and represent it using Java collections and arrays.

Consider a file named students_marks.txt with the following content:

This file signifies a 2D table where each row denotes a student's scores across four subjects. In Java, you can represent this data using a List of int[] to store each row as an array of integers.

To start, we utilize Files.readAllLines(Paths.get("students_marks.txt")) to read all lines from the file. This method retrieves each line and stores it in a List<String>.

Here, Files.readAllLines(filePath) opens and reads the file content into a list of strings, with each item representing a line from the file.

Now that we have the lines from the file stored in a List<String>, we'll convert these lines to a usable format, such as a list of integer arrays, by following these steps:

1. Split each line into tokens: Each line is a string with numbers separated by spaces. We'll split each line string into individual number strings using split(" ").

2. Convert tokens to integers: After splitting the strings, we'll convert each token into an integer using Integer.parseInt. This transforms the string representations of numbers into integers.

Let's transform each line to an array of integers and then compile these arrays into a list:

This code snippet iterates over each line, splits the line into tokens, converts each token to an integer, and stores it in an integer array, which is then added to a list.

In Java, the students_marks.txt content is stored in a List<int[]>, representing the table as rows and columns:

• Row indices: Access rows using the list’s index, e.g., data.get(index).
• Column indices: Access columns within a row using the array index, e.g., data.get(rowIndex)[columnIndex].

The data structure ensures each row corresponds to a line from the file, and each array element corresponds to a number in that line.

To validate our process, we will print the 2D list structure using Java's standard printing mechanisms.

This segment uses nested loops to iterate through each row and print each number in the row space-separated.

Expected Output:

In this lesson, we explored how to parse table data from a file using Java. We utilized Files.readAllLines for file input and parsed data into a List<int[]> for convenient manipulation. Understanding file input handling and data representation in structured formats like lists and arrays is vital in many practical programming scenarios.

You're now ready to proceed to the practice exercises. These exercises will reinforce your new knowledge by encouraging you to apply similar techniques to other file formats and sizes, enhancing your skills in structured data manipulation in Java. Enjoy the hands-on experience, and see you in the next lesson!