正则表达式：
基本概念
方法摘要 static Pattern compile(String regex) static Pattern compile(String regex,int flags) Matcher matcher(CharSequence input)
方法摘要 boolean matches() 匹配整个字符串 boolean find() 找字串 Matcher reset() boolean lookingAt() String group() int start() int end() Matcher appendReplacement(StringBuffer sb,String replacement) StringBuffer appendTail(StringBuffer sb)
使用方法：
private static void demo1() {
Pattern p = Pattern.compile ("[A-Z]{3}" )
Matcher matcher = p.matcher ("BaD" )
System.out .println (matcher.matches ())
System.out .println ("BaD" .matches ("[A-Z]{3}" ))
}数量词: {} * + ?
private static void demo2 () {
System.out .println("aaa" .matches("a+" ));
System.out .println("aaa" .matches("a?" ));
System.out .println("aaa" .matches("a{3,5}" ));
System.out .println("" .matches("a*" ));
System.out .println("aaa" .matches("aa" ));
}数量词 a+ a出现1次或以上 a* a出现0次或以上 a？ a出现0次或1次 a{n} a出现n次 a{n，} a出现n次或以上 a{n，m} a出现[n,m]次
字符类: [] && |
private static void demo3() {
System.out .println ("a" .matches ("[abc]" ))
System.out .println ("a" .matches ("[^abc]" ))
System.out .println ("A" .matches ("[a-zA-Z]" ))
System.out .println ("A" .matches ("[a-z]|[A-Z]" ))
System.out .println ("A" .matches ("[a-z[A-Z]]" ))
System.out .println ("R" .matches ("[A-Z&&[RFG]]" ))
}字符类 [a-zA-Z] [a-z[A-Z]]; A-Z&&[RFG] R,F,G [a-z&&[^m-p]] a 到 z，而非 m 到 p：[a-lq-z]
边界匹配: \b ^ $
private static void demo4() {
System.out .println ("hello sir" .matches ("^hr$" ))
System.out .println ("hello sir" .matches ("^h" ))
System.out .println ("hello sir" .matches ("r$" ))
System.out .println ("hello sir" .matches ("\\w+" ))
System.out .println ("hello sir" .matches ("^h.*r$" ))
System.out .println ("hello sir" .matches ("^h.*o\\b.*r$" ))
}预定义字符: . \d \s \w
private static void demo5() {
System.out .println ("abc888&^%" .matches ("[a-z]{1,3}\\d+[&^#%]+" ))
System.out .println (("\\" .matches ("\\\\" )))
System.out .println (" \n" .matches ("^[\\s&&[^\\n]]*\\n$" ))
}预定义字符 . 任何字符（与行结束符可能匹配也可能不匹配）[\s\S] \d 数字：[0-9] \s 空白字符：[ \t\n\x0B\f\r] \w 单词字符：[a-zA-Z_0-9] \D 非数字：[^0-9] \S 非空白字符：[^\s] \W 非单词字符：[^\w]
字符串查找：matches find lookingAt
lookingAt():从头找； matches():匹配整个字符串； find():找字串； matches()和find()相互影响，记得reset(); private static void demo6() {
Pattern p = Pattern.compile ("\\d{3,5}" )
String s = "123-34345-234-00"
Matcher m = p.matcher (s)
System.out .println (m.matches ())
m.reset ()
System.out .println (m.find ())
System.out .println (m.start () + "-" + m.end ())
System.out .println (m.find ())
System.out .println (m.start () + "-" + m.end ())
System.out .println (m.find ())
System.out .println (m.start () + "-" + m.end ())
System.out .println (m.find ())
//System.out .println (m.start () + "-" + m.end ())
System.out .println (m.lookingAt ())
System.out .println (m.lookingAt ())
System.out .println (m.lookingAt ())
System.out .println (m.lookingAt ())
}字符串替换
private static void demo7 () {
Pattern p = Pattern.compile("java" , Pattern.CASE_INSENSITIVE);
Matcher m = p.matcher("java Java JAVa JaVa IloveJAVA you hateJava afasdfasdf" );
StringBuffer buf = new StringBuffer();
int i=0 ;
while (m.find()) {
i++;
if (i%2 == 0 ) {
m.appendReplacement(buf, "java" );
} else {
m.appendReplacement(buf, "JAVA" );
}
}
m.appendTail(buf);
System.out .println(buf);
}
标志位简写
private static void demo8 () {
Pattern p = Pattern.compile("java" , Pattern.CASE_INSENSITIVE);
System.out .println("Java" .matches("(?i)(java)" ));
}正则表达式分组：group()
private static void demo9 () {
Pattern p = Pattern.compile("\\d{3,5}[a-z]{2}" );
String s = "123aa-34345bb-234cc-00" ;
Matcher m = p.matcher(s);
while (m.find()) {
System.out .println(m.group ());
}
Pattern p1 = Pattern.compile("(\\d{3,5})([a-z]{2})" );
Matcher m1 = p1.matcher(s);
while (m1.find()) {
System.out .println(m1.group (1 ));
System.out .println(m1.group (2 ));
}
}反向引用
private static void demo10() {
Pattern p = Pattern.compile ("(\\d(\\d))\\2" )
String s = "122"
Matcher m = p.matcher (s)
System.out .println (m.matches ())
Pattern p1 = Pattern.compile ("(\\d\\d)\\1" )
String s1 = "1212"
Matcher m1 = p1.matcher (s1)
System.out .println (m1.matches ())
}零宽断言
private static void demo11 () {
String s = "444a66b" ;
Pattern p = Pattern.compile(".{3}(?=a)" );
Pattern p = Pattern.compile("(?=a).{3}" );
Pattern p = Pattern.compile("(?!a).{3}" );
Pattern p = Pattern.compile(".{3}(?!a)" );
Pattern p = Pattern.compile(".{3}(?<=a)" );
Pattern p = Pattern.compile("(?<=a).{3}" );
Pattern p = Pattern.compile("(?<!a).{3}" );
Pattern p = Pattern.compile(".{3}(?<!a)" );
Matcher m = p.matcher(s);
while (m.find()) {
System.out .println(m.group ());
}
}零宽断言 (?=) lookahead 正断言 (?<=) lookbehind 正断言 (?!) lookahead 负断言 (?<!) lookbehind 负断言
解释(?=)： Pattern p = Pattern.compile("^(?=<)<[^>]+>\\w+");
String s = "<div>antzone";
Matcher m = p.matcher(s);
while(m.find()) {
System.out.println(m.group());
}
匹配过程如下: 所在的位置右侧 必须是字符”<”，位置0的右侧恰好是字符”<”，匹配成功，然后控制权转交个”<”,由于”(?=<)”也是零宽的，所以它也是从位置0处开始匹配，于是匹配成功
解释(?!)： Pattern p = Pattern.compile("ab(?![A-Z])");
String s = "abZW863ab88";
Matcher m = p.matcher(s);
while(m.find()) {
System.out.println(m.group());
}
匹配过程如下:
解释(?<=)：` Pattern p = Pattern.compile("(?<=\\bre)\\w+\\b"); //ading
String s = "reading a book";
Matcher m = p.matcher(s);
while(m.find()) {
System.out.println(m.group());
}`
匹配模式
private static void demo12() {
Pattern p = Pattern.compile (".{3,10}[0-9]" )
Pattern p1 = Pattern.compile (".{3,10}?[0-9]" )
Pattern p2 = Pattern.compile (".{3,10}+[0-9]" )
String s = "aaaa5bbbb8"
Matcher m = p.matcher (s)
if (m.find ())
System.out .println (m.start () + "-" + m.end ())
else
System.out .println ("not match!" )
Matcher m1 = p1.matcher (s)
if (m1.find ())
System.out .println (m1.start () + "-" + m1.end ())
else
System.out .println ("not match!" )
Matcher m2 = p2.matcher (s)
if (m2.find ())
System.out .println (m2.start () + "-" + m2.end ())
else
System.out .println ("not match!" )
}
匹配模式 Greedy 长匹配，不满足再往外吐 默认模式 Reluctant 短匹配 ？跟在匹配次数后之后 Possessive 长匹配，不满足不吐，直接返回找不到 +
常用匹配
匹配空白行：Pattern.compile("^[\\s&&[\\n]]*\\n$"); 匹配邮件地址：Pattern.compile("[\\w[.-]]+@[\\w[.-]]+\\.[\\w]+"); 匹配标签中内容：Pattern.compile("(?<=<(\\w+)>).*(?=<\\/\\1>)"); //error:Look-behind group does not have an obvious maximum length near index 10(lookbehind 其中所指定的字符必须是指定数量的，不能用 * + 之类的，但可以用 {0, 100} 这种确定型的。 解决办法：Pattern p=Pattern.compile("(?<=<(\\w{0,"+(Integer.MAX_VALUE-1)+"})>).*(?=<\\/\\1>)"); lookahead 没有这种限制。)
应用：代码统计小程序
package learn;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class MyLearn {static long whileline = 0 ;
static long codeline = 0 ;
static long commentline = 0 ;
public static void main (String[] args) {
String path = "F:\\eclipseworkspace\\mobilesafe\\src\\com\\example\\mobilesafe\\activity" ;
File f = new File(path);
File[] listFiles = f.listFiles();
for (File file : listFiles) {
if (file.getName().matches(".*\\.java$" )) {
parse(file);
}
}
System.out.println("codeLines:" + codeline);
System.out.println("whiteLines:" + whileline);
System.out.println("commentLines:" + commentline);
}
private static void parse (File file) {
BufferedReader br = null ;
boolean commentFlag = false ;
try {
br = new BufferedReader(new FileReader(file));
String line = "" ;
while ((line = br.readLine()) != null ) {
line = line.trim();
if (line.matches("^[\\s&&[^\\n]]*" )) {
whileline++;
} else if (line.startsWith("/*" ) && !line.endsWith("*/" )) {
commentline++;
commentFlag = true ;
} else if (line.startsWith("/*" ) && line.endsWith("*/" )) {
commentline++;
} else if (commentFlag == true ) {
commentline++;
if (line.endsWith("*/" )) {
commentFlag = false ;
}
} else if (line.startsWith("//" )) {
commentline++;
} else {
codeline++;
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (br != null ) {
try {
br.close();
br = null ;
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
扫一扫
10万+
被折叠的 条评论
为什么被折叠?
到【灌水乐园】发言
