Understanding Relative File Paths

In these Java examples, we define a path to the EQs_last_last_week_of_2021.csv file. The data file is within the geological directory, which is within the data-files directory.

– case where the data-files directory is in the current directory
String filePath = "./data-files/geological/EQs_last_week_of_2021.csv";

– case where the data-files directory up one level (in the parent directory)
String filePath = "../data-files/geological/EQs_last_week_of_2021.csv";

– case where the data-files directory is up two levels (in the grandparent directory)
String filePath = "../../data-files/EQs_last_week_of_2021.csv";

– case where the data-files directory is up three levels (in the great grandparent directory)
String filePath = "../../../data-files/EQs_last_week_of_2021.csv";

Let’s take this example further. We are writing code that accesses a data file (called EQs_last_last_week_of_2021.csv) and reads the earthquake data, one line (one earthquake) at a time. The file is a .csv, which means that values are separated by commas (comma separated values).

Which file path will work? It depends on the file structure.

In figure 1, we use:
String filePath = “../../../data-files/geological/EQs_last_week_of_2021.csv”;

Notice that:

1) The ReadData.java file is inside the BuffemaroonReader-example directory. (current level)

2) The buffemaroonreader-class-examples directory is inside the java-examples directory. (up one level)

3) The java-examples directory is inside the programming-with-data-files directory. (up two levels)

4) The programming-with-data-files directory is in the same directory as the data-files directory. (up three levels)

In figure 2, we use:
String filePath = “../../data-files/geological/EQs_last_week_of_2021.csv”;

Notice that:

5) The ReadData.java file is inside the BuffemaroonReader-example directory. (current level)

6) The buffemaroonreader-class-examples directory is inside the java-examples directory. (up one level)

7) The java-examples directory is in the same directory as the data-files directory. (up two levels)

In figure 3, we use:
String filePath = “../data-files/geological/EQs_last_week_of_2021.csv”;

Notice that:

8) The ReadData.java file is inside the BuffemaroonReader-example directory.

9) The buffemaroonreader-class-examples directory is inside the java-examples directory, which is in the same directory as the data-files directory. (up one level)

By the way, this structure seen in Figure 3 is not good practice. It is silly to put the data-files directory in the java-examples directory because a data file can be accessed using any old programming language. With the data-files directory here in the java-examples directory, it would be a pain to access a data file from files within the python-examples directory.

In figure 4, we use:
String filePath = “./data-files/geological/EQs_last_week_of_2021.csv”;

Notice that:

10) The ReadData.java file and the data-files directory are both inside the programming-with-data-files directory. (current level)