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

Exercise 17-2: Loop through and print every character of a String one at a time.
String message = " a bunch of text here. ";
for (int i = 0; i < _____________ ); i + + ) {
}
char c = ________________ ;
println(c);
We can also change a String to all uppercase (or lowercase) using the toUpperCase( ) method.
String uppercase = message.toUpperCase() ;
println(uppercase);
Text 307
You might notice something a bit odd here. Why didn’t we simply say “ message.toUpperCase( ) ” and then
print the “ message ” variable? Instead, we assigned the result of “ message.toUpperCase( ) ” to a new variable
with a diff erent name— “ uppercase ” .
Th is is because a String is a special kind of object. It is immutable . An immutable object is one whose data
can never be changed. Once we create a String , it stays the same for life. Any time we want to change the
String , we have to create a new one. So in the case of converting to uppercase, the method toUpperCase( )
returns a copy of the String object with all caps.
Th e last method we will cover in this chapter is equals( ) . You might fi rst think to compare Strings using
the “ = = ” operator.
String one = " hello";
String two = " hello";
println(one = = two);
Technically speaking, when “ � � ” is used with objects, it compares the memory addresses for each object.
Even though each string contains the same data— “ hello ” —if they are diff erent object instances, then
“ � � ” could result in a false comparison. Th e equals( ) function ensures that we are checking to see if two
String objects contain the exact same sequence of characters, regardless of where that data is stored in the
computer’s memory.
String one = " hello";
String two = " hello";
println(one.equals(two));
Although both of the above methods return the correct result, it is safer to use equals( ) . Depending on
how String objects are created in a sketch, “ � � ” will not always work.