As we all know, in the process of development, it is inevitable to encounter the need to match, find, replace, infer the occurrence of strings, and these circumstances are sometimes more complex, assuming that the pure coding method of solving, often wasting the time and energy of the program ape. Therefore, the study and use of the principle of the form, it has become the main means to solve this contradiction.
As we all know, the canonical form is a specification that can be used for pattern matching and substitution, and a canonical form is a text pattern consisting of ordinary characters (such as characters A through Z) and special characters (metacharacters), which describe one or more strings to be matched when looking for a text body. The regular form is used as a template to match a character pattern to the searched string.
Since the launch of the Java.util.regex package, jdk1.4 has provided us with a very good Java-like application platform.
As the regular form is a very complex system, so I just cite some of the concepts of entry, many others please refer to the relevant books and self-exploration.
Back slash
/t interval ('/u0009 ')
/N line break ('/u000a ')
/R Enter ('/u000d ')
/d number equivalent to [0-9]
/d non-numeric equivalent to [^0-9]
/s blank sign [/T/N/X0B/F/R]
/S non-blank symbol [^/T/N/X0B/F/R]
/w individual characters [a-za-z_0-9]
/w non-individual characters [^a-za-z_0-9]
/F page Break
/e Escape
/b The boundary of a word
/b A non-word boundary
/g the end of a previous match
^ Opening for the limit
^java conditions are limited to Java as the starting character
$ for Limit End
java$ conditions are limited to Java-terminated characters
. Conditional restriction in addition to/n arbitrary a single character
Java.. The condition is limited to Java after two characters in addition to line break
Add specific Restrictions "[]"
[A-Z] condition is limited to one character in the lowercase a to Z range
[A-Z] condition is limited to one character in the uppercase A to Z range
[A-za-z] Condition limited to one character in lowercase A to Z or uppercase A to Z range
[0-9] conditions limited to one character in the lowercase 0 to 9 range
[0-9a-z] conditions are limited to one character in the lowercase 0 to 9 or a to Z range
[0-9[a-z]] condition limited to one character (intersection) in lowercase 0 to 9 or a to Z range
[] Add ^ after add again limit condition "[^]"
[^a-z] Condition limited to one character in the non-lowercase a to Z range
[^a-z] condition is limited to one character in the non-uppercase A to Z range
[^a-za-z] conditions are limited to one character in the range of non-lowercase A to Z or uppercase A to Z
[^0-9] Condition limited to one character in a non-lowercase 0 to 9 range
[^0-9a-z] conditions are limited to one character in a non-lowercase 0 to 9 or a to Z range
[^0-9[a-z]] condition limited to one character (intersection) in non-lowercase 0 to 9 or a to Z range
"*" can be used if the limit is more than 0 times for a specific character
J* more than 0 J
. * More than 0 random characters
J.*d 0 or more random characters between J and D
"+" can be used if the limit is more than 1 times for a specific character
j+ more than 1 J
. + More than 1 random characters
J.+d 1 or more random characters between J and D
"?" can be used when the limit is 0 or 1 times for a specific character
MAX J or Ja appears
Limit to consecutive occurrences of the specified number of characters "{a}"
J{2} JJ
J{3} JJJ
Text more than a, and "{a,}"
J{3,} jjj,jjjj,jjjjj,??? (3 times above J co-exist)
More than one word, B below "{a,b}"
j{3,5} JJJ or JJJJ or JJJJJ
Take a "|" of both.
j| A J or a
java| Hello java or hello
A combination type is specified in "()"
For example, I query <a href=/"index.html/" >index</a> <a href></a> between the data, can write <a.*href=/". * *" > (. +?) </a>
When using the Pattern.compile function, you can increase the number of parameters that control the matching behavior of the normal table:
Pattern Pattern.compile (String regex, int flag)
The value range for flag is as follows:
Pattern.canon_eq The match is determined only if the "normal decomposition (canonical decomposition)" of the two characters is the same in all cases. For example, after using this flag, the expression "a/u030a" will match "?". By default, "canonical equality (canonical equivalence)" is not considered.
Pattern.case_insensitive (? i) by default, the matching of uppercase and lowercase ambiguity is only applicable to the US-ASCII character set. This flag allows the expression to ignore uppercase and lowercase for matching. To match a Unicode character to an unknown size, simply combine the unicode_case with this symbol.
Pattern.comments (? x) in such a pattern, the match is ignored (in the form of the) empty characters (translator Note: Not refers to the expression "//s", but refers to the expression of the Space, tab, enter and so on). Gaze from the beginning, until the end of the line. The ability to enable UNIX line mode through embedded flags.
Pattern.dotall (? s) in such a mode, the expression '. ' Ability to match random characters, including the Terminator that represents a line. By default, the expression '. ' Does not match the terminator of the row.
Pattern.multiline
(? m) in such a mode, ' ^ ' and ' $ ' match the beginning and end of a line, respectively. Also, ' ^ ' still matches the beginning of the string, ' $ ' also matches the end of the string. By default, these two expressions match only the beginning and end of a string.
Pattern.unicode_case
(? u) in this mode, assuming that you also have the CASE_INSENSITIVE flag enabled, it matches the Unicode characters in uppercase and lowercase. By default, uppercase and lowercase insensitive matches apply only to the US-ASCII character set.
Pattern.unix_lines (? d) in this mode, only '/n ' is considered a line abort and is matched with '. ', ' ^ ', and ' $ '.
Throw away the empty concept, and write a few simple Java regular use cases as follows:
For example, when a string includes validation
Find a string that starts with Java and ends at random
Pattern pattern = pattern.compile ("^java.*");
Matcher Matcher = Pattern.matcher ("Java is not human");
Boolean b= matcher.matches ();
Returns True when the condition is satisfied, otherwise false
System.out.println (b);
When you are cutting strings in multiple conditions
Pattern pattern = Pattern.compile ("[, |] +");
string[] STRs = Pattern.split ("Java Hello World java,hello,,world| Sun ");
for (int i=0;i<strs.length;i++) {
System.out.println (Strs[i]);
}
Text substitution (the first occurrence of a character)
Pattern pattern = Pattern.compile ("N-form");
Matcher Matcher = Pattern.matcher ("The regular form Hello World," the statement is the "Hello World");
Replace the first data that matches the regular one
System.out.println (Matcher.replacefirst ("Java"));
Text substitution (All)
Pattern pattern = Pattern.compile ("N-form");
Matcher Matcher = Pattern.matcher ("The regular form Hello World," the statement is the "Hello World");
Replace the first data that matches the regular one
System.out.println (Matcher.replaceall ("Java"));
Text substitution (substitution characters)
Pattern pattern = Pattern.compile ("N-form");
Matcher Matcher = Pattern.matcher ("The regular form Hello World," the statement is the "Hello World");
StringBuffer sbr = new StringBuffer ();
while (Matcher.find ()) {
Matcher.appendreplacement (SBR, "Java");
}
Matcher.appendtail (SBR);
System.out.println (Sbr.tostring ());
Verify that you are an e-mail address
String str= "[email protected]";
Pattern pattern = Pattern.compile ("[//w//.//-][email protected] ([//w//-]+//.) +[//w//-]+ ", pattern.case_insensitive);
Matcher Matcher = Pattern.matcher (str);
System.out.println (Matcher.matches ());
Remove HTML tags
Pattern pattern = pattern.compile ("<.+?>", Pattern.dotall);
Matcher Matcher = Pattern.matcher ("<a href=/" index.html/"> Home </a>");
String string = Matcher.replaceall ("");
System.out.println (string);
Find the appropriate conditional string in HTML
Pattern pattern = pattern.compile ("href=/" (. +?) /"");
Matcher Matcher = Pattern.matcher ("<a href=/" index.html/"> Home </a>");
if (Matcher.find ())
System.out.println (Matcher.group (1));
}
Intercept/HTTP Address
Intercepting URLs
Pattern pattern = Pattern.compile ("(http://|https://) {1}[//w//.//-/:]+");
Matcher Matcher = Pattern.matcher ("dsdsdsStringBuffer buffer = new StringBuffer ();
while (Matcher.find ()) {
Buffer.append (Matcher.group ());
Buffer.append ("/r/n");
System.out.println (Buffer.tostring ());
}
Replace the text in the specified {}
String str = "Java is now in the history of {0} years-{1} years";
String[][] object={new string[]{"//{0//}", "1995"},new string[]{"//{1//}", "2007"};
SYSTEM.OUT.PRINTLN (replace (str,object));
public static string replace (final String sourcestring,object[] Object) {
String temp=sourcestring;
for (int i=0;i<object.length;i++) {
String[] result= (string[]) object[i];
Pattern pattern = pattern.compile (result[0]);
Matcher Matcher = pattern.matcher (temp);
Temp=matcher.replaceall (result[1]);
}
return temp;
}
Querying a file under a specified folder with regular conditions
For cache file List
Private ArrayList files = new ArrayList ();
Used to host file paths
Private String _path;
Used to host a regular formula that is not merged
Private String _regexp;
Class Myfilefilter implements FileFilter {
/**
* Matching file name is called
*/
Public boolean accept (file file) {
try {
Pattern pattern = pattern.compile (_REGEXP);
Matcher match = Pattern.matcher (File.getname ());
return match.matches ();
} catch (Exception e) {
return true;
}
}
}
/**
* Parse input stream
* @param inputs
*/
Filesanalyze (String path,string regexp) {
GetFileName (PATH,REGEXP);
}
/**
* Analyze file names and add files
* @param input
*/
private void GetFileName (String path,string regexp) {
Folder
_path=path;
_regexp=regexp;
File directory = new file (_path);
file[] Filesfile = directory.listfiles (New Myfilefilter ());
if (Filesfile = = null) return;
for (int j = 0; J < Filesfile.length; J + +) {
Files.add (Filesfile[j]);
}
Return
}
/**
* Display output information
* @param out
*/
public void print (PrintStream out) {
Iterator elements = Files.iterator ();
while (Elements.hasnext ()) {
File file= (file) Elements.next ();
Out.println (File.getpath ());
}
}
public static void Output (String path,string regexp) {
Filesanalyze fileGroup1 = new Filesanalyze (PATH,REGEXP);
Filegroup1.print (System.out);
}
public static void Main (string[] args) {
Output ("c://", "[a-z|.] *");
}
Java regular function is very much, in fact, only if the character processing, there is no regular do not do things exist. (Of course, the regular explanation is more time-consuming. | | | ...... ）
Getting started with the Java regularization table
