Arrays and Strings - Beginning Java - page 196

This statement deletes the substring "the " from phrase , so it then contains the string "When bats come
in" .
You can completely reverse the sequence of characters in a StringBuffer object with the reverse()
method. For example, if you define the object with the declaration
StringBuffer palindrome = new StringBuffer("so many dynamos");
you can then transform it with the statement:
palindrome.reverse();
which results in palindrome containing the useful phrase “ somanyd ynam os ”.
Creating a String Object from a StringBuffer Object
You can produce a String object from a StringBuffer object by using the toString() method of the
StringBuffer class. This method creates a new String object and initializes it with the string contained in
the StringBuffer object. For example, to produce a String object containing the proverb that you created
in the previous section, you could write:
String saying = proverb.toString();
The object saying contains "Many hands make light work" .
The toString() method is used extensively by the compiler together with the append() method to im-
plement the concatenation of String objects.
Suppose you have the following strings defined:
String str1 = "Many", str2=" hands", str3=" make", str4=" light", str5=" work.";
When you write a statement such as
String saying = str1 + str2 + str3 + str4 + str5;
the compiler implements this as:
String saying = new StringBuffer().append(str1).append(str2).
append(str3).append(str4).
append(str5).toString();
The expression to the right of the = sign is executed from left to right, so the segments of the string encap-
sulated by the objects are appended to the StringBuffer object that is created until finally the toString()
method is invoked to convert it to a String object. String objects can't be modified, so any alteration or
extension of a String object involves the use of a StringBuffer object, which can be changed.
It's time to see a StringBuffer object in action.