Learning Processing: A Beginner's Guide to Programming Images ...

330 Learning Processing
We are going to follow this model in this section, working with the simplest means of data retrieval:
reading from a text fi le. Text fi les can be used as a very simple database (we could store settings for a
program, a list of high scores, numbers for a graph, etc.) or to simulate a more complex data source.
In order to create a text fi le, you can use any simple text editor. Windows Notepad or Mac OS X
TextEdit will do, just make sure you format the fi le as “ plain text. ” It is also advisable to name the text
fi les with the “ .txt ” extension, just to avoid any confusion. And just as with image fi les in Chapter 15,
these text fi les should be placed in the sketch’s “ data ” directory in order for them to be recognized by the
Processing sketch.
Once the text fi le is in place, Processing ’s loadStrings( ) function is used to read the content of the fi le into
a String array. Th e individual lines of text in the fi le (see Figure 18.2) each become an individual element
in the array.
fi g 18.2
String[] lines = loadStrings(" file.txt " );
println( " there are " + lines.length + " lines " );
for (int i = 0; i < lines.length; i + + ) {
println(lines[i]);
}
To run the code, create a text fi le called “ fi le.txt ” , type a bunch of lines in that fi le, and place it in your
sketch’s data directory.
Exercise 18-6: Rewrite Example 17-3 so that it loads the headlines from a text fi le.
Text from a data fi le can be used to generate a simple visualization. In Example 18-2, loads data fi le
shown in Figure 18.3 . Th e results of visualizing this data are shown in Figure 18.4 .
fi g. 18.3 Contents of “Data.txt”
This code will print all the lines from the
source text fi le. Shown in Figure 18.2.