Arrays and Strings - Beginning Java 2 SDK - page 158

Adding to a StringBuffer Object
The append() method enables you to add a string to the end of the existing string stored in a
StringBuffer object. This method comes in quite a few flavors, but perhaps the simplest adds a
String constant to a StringBuffer object.
If we have defined a StringBuffer object with the statement:
StringBuffer aString = new StringBuffer("A stitch in time");
we can add to it with the statement:
aString.append(" saves nine");
after which aString will contain " A stitch in time saves nine ". The length of the string
contained in the StringBuffer object will be increased by the length of the string that you add. You
don't need to worry about running out of space though. If necessary, the capacity will be increased
automatically to accommodate the longer string.
The append() method returns the extended StringBuffer object, so you could also assign it to
another StringBuffer object. Instead of the previous statement, you could have written:
StringBuffer bString = aString.append(" saves nine");
Now both aString and bString point to the same StringBuffer object.
If you take a look at the operator precedence table back in Chapter 2, you will see that the ' . ' operator
(sometimes called the member selection operator) that we use to execute a particular method for an
object has left-to-right associativity. You could therefore write:
StringBuffer proverb = new StringBuffer(); // Capacity is 16
proverb.append("Many").append(" hands").append(" make").
append(" light").append(" work.");
The second statement is executed from left to right, so that the string contained in the object proverb
is progressively extended until it contains the complete string.
Appending a Substring
Another version of the append() method will add part of a String object to a StringBuffer
object. This version of append() requires you to specify two additional arguments: the index position
of the first character to be appended, and the total number of characters to be appended. This operation
is shown in the following diagram.