Java regular expression learning:
because the regular expression is a very complex system, to name just a few examples of this concept of entry, more please refer to the relevant books and explore on their own.
// backslash
/ t interval ( '/ u0009')
/ n-line feed ( '/ u000A')
/ R & lt carriage return ( '/ u000D')
/ D digital equivalent to [0-9]
/ D non-digital equivalent of to [^ 0-9]
/ white symbol S [/ T / n-/ x0B / F / R & lt]
/ non-blank symbol S [^ / T / n-/ x0B / F / R & lt]
/ W single character [a-zA- Z ~ 0-9]
/ W is a non-single character [^ a-zA-Z ~ 0-9]
/ feed character F
/ E the Escape
/ a word boundary B
/ B a non-word boundary
before / G a matching end
^ as limiting beginning
^ java conditions begin to Java-character
$ as limiting end
java $ java conditions of ending characters in
. addition to the conditions / n at any single character a
java .. conditions after two java any change except line characters
include specific restrictions "[]"
[az] conditions in lowercase a to z in a range of characters
[AZ] conditions in upper case a to z in a range of characters
[a-zA-Z] conditions a to z in lowercase or uppercase A to Z in the range of a character
[0-9] conditions in the range 0 to 9 in lowercase character
[0-9a-z] conditions in lowercase 0 to 9 or in a range a to z character
[0-9 [az]] conditions in lowercase 0 to 9 or in a range a to z character (intersection)
was added in [] ^ restrictions again after adding '[^ ] "
[^ az] conditions in a non-lowercase a to z range of a character
[^ AZ] conditions in a non-uppercase a to a character Z range
[^ a-zA-Z] conditions in a non-lowercase a to z or uppercase a to Z in a range of characters
[^ 0-9] conditions in a non-lowercase range of 0 to 9, a character
[^ 0-9a-z] conditions in a non-lowercase 0 to 9 or in a range a to z character
[^ 0-9 [az]] conditions in the non-lowercase 0 to 9 or a to z in a range of characters (the intersection)
above 0 appearances for a particular character in restrictions, you can use "*"
J * 0 Ge more J
. * 0 or more arbitrary characters
J. * zero or more arbitrary characters between the D and J D
When restrictions occur more than once for a specific character, use the "+"
J + more than 1 J
. + More than an arbitrary character
J. + between D J and D above an arbitrary character
appears there is a specific character restrictions above 0 or 1, can use the "?"
JA? J or JA appears
restricted to consecutive occurrences specified number of characters "{a} '
J {2} JJ
J {. 3} JJJ
text above a th, and" {a, } '
J {3,} JJJ, JJJJ , jJJJJ, ??? ( more than 3 times coexist J)
b less "b words or more, {a,}'
J {3,5} JJJ JJJJ or jjjjj or
both take a "|"
J | a J or a
the Java | or the Java Hello Hello
"()" in the provisions of a combination of type
, for example, I check <a href=/"index.html/"> index </a> in <a href > data between </a>, can be written as <a. * href = / " . * /"> (. +?) </a>
in use Pattern.compile function, may be added to control the behavior of the regular expression matching parameters:
the Pattern of Pattern.compile (String REGEX, int in Flag)
in Flag of the following ranges:
Pattern.CANON_EQ if and only if the case of "regular decomposition (canonical decomposition)" two characters are exactly the same, it finds a match. For example, after using this flag, the expression "a / u030A" will match "?." By default, not considered "canonical equivalence (canonical equivalence)".
Under Pattern.CASE_INSENSITIVE (? I) By default, unknown flu case matching applies only to US-ASCII character set. This flag allows expression match ignoring case. To Unicode characters a sense of unknown size match, as long as UNICODE_CASE with this flag together on the line.
Pattern.COMMENTS (? X) In this mode, ignores (regular expressions) of space characters (Translator's Note match: No, not expressions of "// s", but refers to expressions of space, tab, carriage return and the like). # Comments from the beginning until the end of the line. Unix-line mode can be enabled via the embedded flag.
Pattern.DOTALL (? S) In this mode, the expression '' matches any character, including a line terminator represented. By default, the expression '' does not match the line terminators.
Pattern.MULTILINE
(? M) In this mode, '^' and '$', respectively match the beginning and end of a line. In addition, '^' still matches the beginning of the string, '$' also matches the end of the string. By default, these two expressions only match the beginning and end of the string.
Pattern.
UNICODE_CASE (? U) In this mode, if you also enabled CASE_INSENSITIVE flag, then it will Unicode characters unknown flu case matching. By default, case-insensitive match applies only to US-ASCII character set.
Pattern.UNIX_LINES (? D) In this mode, only the '/ n' suspension was only recognized as a line, and matched with '.', '^', And '$'.
抛开空泛的概念，下面写出几个简单的Java正则用例：
◆比如，在字符串包含验证时
//查找以Java开头,任意结尾的字符串
Pattern pattern = Pattern.compile("^Java.*");
Matcher matcher = pattern.matcher("Java不是人");
boolean b= matcher.matches();
//当条件满足时，将返回true，否则返回false
System.out.println(b);
◆以多条件分割字符串时
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]);
}
◆文字替换（首次出现字符）
Pattern pattern = Pattern.compile("正则表达式");
Matcher matcher = pattern.matcher("正则表达式 Hello World,正则表达式 Hello World");
//替换第一个符合正则的数据
System.out.println(matcher.replaceFirst("Java"));
◆文字替换（全部）
Pattern pattern = Pattern.compile("正则表达式");
Matcher matcher = pattern.matcher("正则表达式 Hello World,正则表达式 Hello World");
//替换第一个符合正则的数据
System.out.println(matcher.replaceAll("Java"));
◆文字替换（置换字符）
Pattern pattern = Pattern.compile("正则表达式");
Matcher matcher = pattern.matcher("正则表达式 Hello World,正则表达式 Hello World ");
StringBuffer sbr = new StringBuffer();
while (matcher.find()) {
matcher.appendReplacement(sbr, "Java");
}
matcher.appendTail(sbr);
System.out.println(sbr.toString());
◆验证是否为邮箱地址
String str="[email protected]";
Pattern pattern = Pattern.compile("[//w//.//-]+@([//w//-]+//.)+[//w//-]+",Pattern.CASE_INSENSITIVE);
Matcher matcher = pattern.matcher(str);
System.out.println(matcher.matches());
◆去除html标记
Pattern pattern = Pattern.compile("<.+?>", Pattern.DOTALL);
Matcher matcher = pattern.matcher("<a href="/" mce_href="/""index.html/">主页</a>");
String string = matcher.replaceAll("");
System.out.println(string);
◆查找html中对应条件字符串
Pattern pattern = Pattern.compile("href=/"(.+?)/"");
Matcher matcher = pattern.matcher("<a href="/" mce_href="/""index.html/">主页</a>");
if(matcher.find())
System.out.println(matcher.group(1));
}
◆截取http://地址
//截取url
Pattern pattern = Pattern.compile("(http://|https://){1}[//w//.//-/:]+");
Matcher matcher = pattern.matcher("dsdsds<http://dsds//gfgffdfd>fdf");
StringBuffer buffer = new StringBuffer();
while(matcher.find()){
buffer.append(matcher.group());
buffer.append("/r/n");
System.out.println(buffer.toString());
}
◆替换指定{}中文字
String str = "Java目前的发展史是由{0}年-{1}年";
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;
}
◆以正则条件查询指定目录下文件
//用于缓存文件列表
private ArrayList files = new ArrayList();
//用于承载文件路径
private String _path;
//用于承载未合并的正则公式
private String _regexp;
class MyFileFilter implements FileFilter {
/**
* 匹配文件名称
*/
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;
}
}
}
/**
* 解析输入流
* @param inputs
*/
FilesAnalyze (String path,String regexp){
getFileName(path,regexp);
}
/**
* 分析文件名并加入files
* @param input
*/
private void getFileName(String path,String regexp) {
//目录
_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;
}
/**
* 显示输出信息
* @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|.]*");
}
Reproduced in: https: //my.oschina.net/lendylongli/blog/226792