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

18
Data Input
“ A million monkeys were given a million typewriters. It’s called the Internet. ”
—Simon Munnery
In this chapter:
– Manipulating Strings.
– Reading and writing text fi les.
– HTTP requests, parsing HTML.
– XML, RSS feeds.
– The Yahoo search API.
– The applet sandbox.
Data Input 325
Th is chapter will move beyond displaying text and examine how to use String objects as the basis for
reading and writing data. We will start by learning more sophisticated methods for manipulating Strings ,
searching in them, chopping them up, and joining them together. Afterward, we will see how these skills
allow us to use input from data sources, such as text fi les, web pages, XML feeds, and third party APIs,
and take a step into the world of data visualization.
18.1
Manipulating Strings
In Chapter 17, we touched on a few of the basic functions available in the Java String class, such as
charAt( ) , toUpperCase( ) , equals( ) , and length( ) . Th ese functions are documented on the Processing
reference page for Strings. Nevertheless, in order to perform some more advanced data parsing
techniques, we will need to explore some additional String manipulation functions documented in the
Java API (more about the Java API to come in Chapter 23).
http://java.sun.com/j2se/1.4.2/docs/api/java/lang/String.html
Let’s take a closer look at the following two String functions: indexOf( ) and substring( ) .
indexOf( ) locates a sequence of characters within a String . It takes one argument, a search String , and
returns a numeric value that corresponds to the fi rst occurrence of the search String inside of the String
being searched.
String search = " def";
String toBeSearched = " abcdefghi";
int index = toBeSearched.indexOf(search);
The value of index
in this example is 3.
Strings are just like arrays, in that the fi rst character is index number zero and the last character is the
length of the String minus one.