A Collection of Useful Classes - Beginning Java 2 SDK - page 582

This will produce the output:
256
16
-2.5
6.25
.243
0.1234
How It Works
Well, we found all the numbers in the string so our regular expression works well, doesn't it? You can't
do that with the methods in the String class. The only new code item here is the method, group() ,
that we call in the while loop for the Matcher object, m . This method returns a reference to a String
object containing the subsequence corresponding to the last match of the entire pattern. Calling the
group() method for the Matcher object, m , is equivalent to the expression
str.substring(m.start(), m.end()) .
Search and Replace Operations
You can implement a search and replace operation very easily using regular expressions. Whenever you
call the find() method for a Matcher object, you can call the appendReplacement() method to
replace the subsequence that was matched. You create a revised version of the original string in a new
String Buffer object. There are two arguments to the appendReplacement() method. The first is a
reference to the StringBuffer object that is to contain the new string, and the second is the
replacement string for the matched text. We can see how this works by considering a specific example.
Suppose we define a string to be searched as:
String joke = "My dog hasn't got any nose.\n"
+"How does your dog smell then?\n"
+"My dog smells horrible.\n";
We now want to replace each occurrence of " dog " in the string by " goat ". We first need a regular
expression to find " dog ":
String regEx = "dog";
We can compile this into a pattern and create a Matcher object for the string joke :
Pattern doggone = Pattern.compile(regEx);
Matcher m = doggone.matcher(joke);
We are going to assemble a new version of joke in a StringBuffer object that we can create like this:
StringBuffer newJoke = new StringBuffer();