Regular Expressions - Beginning Java 8 Fundamentals - page 513

a@k matches the regex .@.
[e-mail] does not match the regex .@.
r@j matches the regex .@.
a%N does not match the regex .@.
.@. matches the regex .@.

Some important points to note are the following:

".@." did not match “ [e-mail] ”, because a dot means
only one character and the String.matches() method matches the pattern in the regular
expression against the entire string. Note that the string "[e-mail]" has the
pattern represented by .@. ; that is, a character followed by @ and another character. However,
the pattern matches part of the string, not the entire string. The "r@j" part of “ webmaster@
jdojo.com" matches that pattern. I will present some examples where you will match the
pattern anywhere in the string rather than match the entire string.

• The regular expression

• If you want to match a dot character in a string, you need to escape the dot in the regular

expression. The regular expression ".\\.." will match any string of three characters
in which the middle character is a dot character. For example, The method call "a.b".
matches(".\\..") will return true ; the method call "...".matches(".\\..") will return
true ; the method calls "abc".matches(".\\..") and "aa.ca".matches(".\\..") will return
false .

You can also replace the matching string with another string. The String class has two methods to do the match
replacement:

String replaceAll(String regex, String replacementString): •

String replaceFirst(String regex, String replacementString):
The replaceAll() method replaces strings, which match the pattern represented by the specified regex , with the
specified replacementString . It returns the new string after replacement. Some examples of using the replaceAll()
method are as follows:

•

String regex = ".@.";

// newStr will contain "webmaste***dojo.com"
String newStr = "[e-mail]".replaceAll(regex,"***");

// newStr will contain "***"
newStr = "A@B".replaceAll(regex,"***");

// newStr will contain "***and***"
newStr = "A@BandH@G".replaceAll(regex,"***");

// newStr will contain "B%T" (same as the original string)
newStr = "B%T".replaceAll(regex,"***");