Arrays and Strings - Beginning Java - page 188

object than just the string that it contains initially, and of course, a string literal is a String object by defin-
ition.
You can also create a StringBuffer object using a reference stored in a variable of type String :
String phrase = "Experience is what you get when you're expecting something
else.";
StringBuffer buffer = new StringBuffer(phrase);
The StringBuffer object, buffer , contains a string that is the same as that encapsulated by the String
object, phrase .
You can just create the StringBuffer variable, in much the same way as you created a String variable:
StringBuffer myString = null;
This variable does not refer to anything until you initialize it with a defined StringBuffer object. For
example, you could write:
myString = new StringBuffer("Many a mickle makes a muckle");
This statement creates a new StringBuffer object encapsulating the string "Many a mickle makes a
muckle" and stores the reference to this object in myString . You can also initialize a StringBuffer vari-
able with an existing StringBuffer object:
StringBuffer aString = myString;
Both myString and aString now refer to a single StringBuffer object.
The Capacity of a StringBuffer Object
The String objects that you have been using each contain a fixed string, and when you create a String
object, memory is allocated to accommodate however many Unicode characters are in the string it encapsu-
lates. Everything is fixed so memory usage is not a problem. A StringBuffer object is a little different. It
contains a block of memory called a buffer , which may or may not contain a string, and if it does, the string
need not occupy the entire buffer. Thus, the length of a string in a StringBuffer object can be different
from the length of the buffer that the object contains. The length of the buffer is referred to as the capacity
of the StringBuffer object.
After you have created a StringBuffer object, you can find the length of the string it contains, by using
the length() method for the object:
StringBuffer aString = new StringBuffer("A stitch in time");
int theLength = aString.length();
If the object aString were defined as in the preceding declaration, the variable theLength would have
the value 16. However, the capacity of the object is larger, as illustrated in Figure 4-12 .
FIGURE 4-12