How to use an expression in Java language programming

Three classes covered by a JAVA regular expression:

String,pattern,matcher

Pattern is the mode to match, and Matcher is the result of the match.

For example: pattern p = Pattern.complie ("[A-z]{3}");

Matcher m = P.mather ("abc");

To match a backslash in a regular expression, use four backslashes to indicate: "\". Matches ("\");

Matches the blank line "n". Matches ("^[\s&&[^\n]]*\n$");

Finds the match result at the beginning and end of the entire string

Pattern p = Pattern.complie ("\d{3,5}");

String a = "123-2135-155-00";

Matcher m = P.matcher (s);

M.matches ()//match the entire string, so here is false;

M.reset ();

while (M.find ())//Find a substring that matches this pattern

{

System.out.println (M.start () + "to" + m.end ());

}

Converts matching Java to uppercase

Pattern p = Pattern.complie ("java", pattern.case_insensitive);

Matcher m = P.matcher ("java java java ilovejava you Hatejava");

M.replaceall ("JAVA");

Converts the number of spouses to uppercase and the odd number to lowercase

Package zx.test;

Import Java.util.regex.Matcher;

Import Java.util.regex.Pattern;

public class Testpattern

{

public static void Main (string[] args)

{

StringBuffer newstring = new StringBuffer ();

String ispatternstring = "Java java java Ilovejava you Hatejava";

Pattern p = pattern.compile ("java", pattern.case_insensitive);

Matcher m = P.matcher (ispatternstring);

int i = 0;

while (M.find ())

{

i++;

if (i% 2 = 0)

{

M.appendreplacement (newstring, "Java");

}

Else

{

M.appendreplacement (newstring, "JAVA");

}

}

M.appendtail (newstring);

System.out.println (newstring);

}

}

Output results: Java Java java Ilovejava you Hatejava

Java Regular expression groupings:

private static void Testgroup ()

{

String s = "3412AFDSAF-34IJII-422342K23-423423FSDFAF";

Pattern p = pattern.compile ("(\d{1,10}) ([a-z]{1,9})"); Group 1: (\d{1,10}) Group 2: ([a-z]{1,9})

Matcher m = P.matcher (s);

while (M.find ())

{

System.out.println ("Group0:" + m.group () + "Group1:" + m.group (1) + "Group2:" + m.group (2));

}

}

Output results:

Group0:3412afdsaf group1:3412 Group2:afdsaf

Group0:34ijii group1:34 Group2:ijii

group0:422342k group1:422342 Group2:k

GROUP0:423423FSDFAF group1:423423 GROUP2:FSDFAF