4. Familiar with Java Basic Class Library series--java Regular Expression class library

Regular expression Syntax structure diagram:

Java Regular Expression class library structure diagram:

Java Typical example

1. String class matches () method

Determine if a string conforms to a specific regular expression

@Test public void Testregex () {String regex = ". *\\d{3}.*"; String str1 = "11tec34"; String str2 = "285DFFD";  String STR3 = "bac7736db";//Output: False, True, TrueSystem.out.println (Str1.matches (regex) + "," + str2.matches (regex) + "," + Str3.matches (regex));}

2. Split () method of String class

To split a string with regular expressions

@Test public void TestRegex2 () {String input = "Hello3world8my9name1is5jacket"; String regex = "\\d";  With a number as the delimiter string strs[] = Input.split (regex);//output: Hello World My Name is jacketfor (String str:strs) {System.out.print (St R + "");} SYSTEM.OUT.PRINTLN (); input = "Hellodogworlddogmydognamedogisdogjacket"; regex = "dog";  With "dog" character as delimiter STRs = Input.split (regex);//output: Hello World My Name is jacketfor (String str:strs) {System.out.print (str + ") ");} }

3. The string class replace () method

Replacing characters with regular expressions

@Test public void TestRegex3 () {String input = "Hello3world8my9name1is5jacket"; String regex = "\\d";  With a number as the delimiter string firststr = Input.replacefirst (Regex, ":"); Replace only the first matching character string allstr = Input.replaceall (Regex, ":");  Replace all matching characters//output://hello:world8my9name1is5jacket//hello:world:my:name:is:jacketsystem.out.println (FIRSTSTR); System.out.println (ALLSTR);}

4. Pattern.matches () static method

Determines whether a string conforms to a regular expression, equivalent to the matches () method of the String class

@Test public void testRegex4 () {String regex1 = "\\bdog\\b"; String regex2 = ". *\\bdog\\b.*"; String input = "Dog dog dog Doggie Dogg";//output: False,truesystem.out.println (pattern.matches (regex1, input) + "," + Pattern. Matches (regex2, input));  }

5, Pattern class split () method

Splits a string according to a regular expression, equivalent to the split () method of the String class

6.split () Split string  -equivalent to the split () method of string @test public void testRegex6 () {string regex = "\\d"; String input = "Hello3world5hello8java"; Pattern p = pattern.compile (regex); String strs[] = p.split (input);//output: Hello World Hello java for (String str:strs) {System.out.print (str + "");}}

6. Pattern.quote () static method

Gets a regular expression that matches this string

@Test public void testRegex6 () {///example 1String input = "."; String regex = pattern.quote (Input), Boolean flag = pattern.matches (regex, input);//output: \q353434\ EtrueSystem.out.println (regex); SYSTEM.OUT.PRINTLN (flag);//Example 2input = "Test.test"; String erroroutput = Input.replaceall (".", "/");//output://///////system.out.println (erroroutput);//Example 3String Correctoutput = Input.replaceall (Pattern.quote ("."), "/");//output: Test/testsystem.out.println (correctoutput);}

7. Matcher class Find () method, Start () method, End () method

@Test public void testRegex7 () {//m.start ()   m.end ()  String regex = "\\bdog\\b"; String input = "Dog dog dog Doggie Dogg"; Pattern p = pattern.compile (regex);     Matcher m = p.matcher (input);        Gets the match object     int count = 0;     while (M.find ()) {            count++;            Match number 1,start (): 0,end (): 3           //match number 2,start (): 4,end (): 7           //match number 3,start (): 8,end (): 11
   system.out.print ("Match number" + count);            System.out.print (", Start ():" + M.start ());            System.out.println (", End ():" + m.end ());}     }

8. Matcher class Find (int index) method, start (int index), end (int index )

@Test public void testRegex8 () {//m.start () m.end () String regex = "\\bdog\\b"; String input = "Dog dog dog Doggie Dogg"; 　　    Pattern p = pattern.compile (regex);        Matcher m = p.matcher (input);  Get the Match object//m.find (int start)//output: Start (): 0,end (): 3//start (): 4,end (): 7 m.find (0);     Start looking for System.out.print ("Start ():" + M.start ()) from the first character of the string to match;     System.out.println ("End ():" + m.end ());    M.find ();     System.out.print ("Start ():" + M.start ());         System.out.println ("End ():" + m.end ());      M.find (int start)//output: Start (): 4,end (): 7//start (): 8,end (): M.find (4);     System.out.print ("Start ():" + M.start ());     System.out.println ("End ():" + m.end ());    M.find ();     System.out.print ("Start ():" + M.start ());         System.out.println ("End ():" + m.end ());    M.start (int group) m.end (int group) m.find (0);//int firststartgroupindex = M.start (0); System.out.println (Firststartgroupindex); }

9. Matcher class Lookingat () method, Matches () method

Determines whether a string matches a specific regular expression, the Lookingat () method does not require a match, and the matches () method requires all matching

@Test public void testRegex9 () {String regex = "Foo"; String str = "fooooooooooooooooo";         Pattern pattern = pattern.compile (regex);         Matcher Matcher = Pattern.matcher (str);          System.out.println ("Current regex is:" + regex);         SYSTEM.OUT.PRINTLN ("Current STR is:" + str);          System.out.println ("Lookingat ():" + Matcher.lookingat ());  True         System.out.println ("matches ():" + matcher.matches ()); False, because matches requires all matches}

There are other methods of matcher that have not been sorted out,

There are other methods of the Matcher class that are not organized:

1.group (int Group) method

2.appendReplacement ()/Appendtail ()/ReplaceAll ()/Replacefirst ()/quotereplacement ()

The Find () method of the 99.Matcher class, the Start () method, and the end () method

　　

More detailed regular expression posts can be found in:

Official Microsoft Documentation: https://msdn.microsoft.com/zh-cn/library/ae5bf541 (v=vs.80). aspx

A good regular expression tutorial: Http://www.java3z.com/cwbwebhome/article/article8/Regex/Java.Regex.Tutorial.html#reg7

4. Familiar with Java Basic Class Library series--java Regular Expression class library