正则表达式初入门
发布时间：2020-12-14 02:22:43 所属栏目：百科 来源：网络整理
导读：常用元字符 代码 说明 . 匹配除换行符以外的任意字符 w 匹配字母或数字或下划线或汉字 s 匹配任意的空白符 d 匹配数字 b 匹配单词的开始或结束 ^ 匹配字符串的开始 $ 匹配字符串的结束 常用限定符 代码/语法 说明 * 重复零次或更多次 + 重复一次或更多次
常用元字符
常用限定符
常用反义词
从java 代码来 一步步 解析
package src;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class test {
public static void main(String[] args) {
//简单认识正则表达式的概念
/*
p("abc".matches("..."));
p("a8729a".replaceAll("d","-"));
Pattern p = Pattern.compile("[a-z]{3}");
Matcher m = p.matcher("fgh");
p(m.matches());
p("fgha".matches("[a-z]{3}"));
*/
//初步认识. * + ?
/*
p("a".matches(".")); //one
p("aa".matches("aa"));
p("aaaa".matches("a*")); //zero or more
p("aaaa".matches("a+")); //one or more
p("".matches("a*"));
p("aaaa".matches("a?")); //zero or best of one
p("".matches("a?"));
p("a".matches("a?"));
p("214523145234532".matches("d{3,100}"));
p("192.168.0.aaa".matches("d{1,3}.d{1,3}"));
p("192".matches("[0-2][0-9][0-9]"));
*/
//范围
/*
p("a".matches("[abc]")); //一个中括号里面匹配一个
p("a".matches("[^abc]")); //取除了abc 之外的其它
p("A".matches("[a-zA-Z]")); //取小写的a-z 或者A-Z
p("A".matches("[a-z]|[A-Z]")); //同上
p("A".matches("[a-z[A-Z]]")); //同上
p("R".matches("[A-Z&&[RFG]]")); //A-Z 之中 并且 是【RFG】之中的3者之1
*/
//认识s w d
// p(" nrt".matches("s{4}"));
// p(" ".matches("S")); //正则表达式中2 个反斜杠才表示转义字符/，
// p("a_8".matches("{3}"));
// p("abc888&^%".matches("[a-z]{1,3}d+[&^#%]+"));
// p("".matches("\")); //由于字符里面,一个反斜杠表示转移，要表示一个反斜杠 java 里面 需要 个，而正则表达式里面，两个才表示一个反斜杠，所以是4个
//POSIX Style
//p("a".matches("p{Lower}"));
//boundary
/*
p("hello sir".matches("^h.*"));
p("hello sir".matches(".*ir$"));
p("hello sir".matches("^h[a-z]{1,3}ob.*"));
p("hellosir".matches("^h[a-z]{1,3}ob.*"));
//whilte lines
p(" n".matches("^[s&&[^n]]*n$"));
p("aaa 8888c".matches(".*d{4}."));
p("aaa 8888c".matches(".*bd{4}."));
p("aaa8888c".matches(".*d{4}."));
p("aaa8888c".matches(".*bd{4}."));
*/
//email
//p("asdfasdfsafsf@dsdfsdf.com".matches("[w[.-]]+@[w[.-]]+.[w]+"));
//matches find lookingAt
/*
Pattern p = Pattern.compile("d{3,5}");
String s = "123-34345-234-00";
Matcher m = p.matcher(s);
p(m.matches());
m.reset();
p(m.find());
p(m.start() + "-" + m.end());
p(m.find());
p(m.start() + "-" + m.end());
p(m.find());
p(m.start() + "-" + m.end());
p(m.find());
//p(m.start() + "-" + m.end());
p(m.lookingAt());
p(m.lookingAt());
p(m.lookingAt());
p(m.lookingAt());
*/
//replacement
/*
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);
p(buf);
*/
//group
/*
Pattern p = Pattern.compile("(d{3,5})([a-z]{2})");
String s = "123aa-34345bb-234cc-00";
Matcher m = p.matcher(s);
while(m.find()) {
p(m.group());
}
*/
//qulifiers
/*
Pattern p = Pattern.compile(".{3,10}+[0-9]");
String s = "aaaa5bbbb68";
Matcher m = p.matcher(s);
if(m.find())
p(m.start() + "-" + m.end());
else
p("not match!");
*/
//non-capturing groups
/*
Pattern p = Pattern.compile(".{3}(?=a)");
String s = "444a66b";
Matcher m = p.matcher(s);
while(m.find()) {
p(m.group());
}
*/
//back refenrences
/*
Pattern p = Pattern.compile("(d(d))2");
String s = "122";
Matcher m = p.matcher(s);
p(m.matches());
*/
//flags的简写
//Pattern p = Pattern.compile("java",Pattern.CASE_INSENSITIVE);
// p("Java".matches("(?i)(java)"));
}
public static void p(Object o) {
System.out.println(o);
}
}
package src;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* Created with IntelliJ IDEA.
* User: swrite
* Date: 13-4-4
* Time: 下午5:41
* To change this template use File | Settings | File Templates.
*/
public class testaction {
private static void p(Object obj){
System.out.println(obj);
}
public static void main(String args[]){
/**
* 认识s w d
p(" nrt".matches("s{4}"));
p(" ".matches("S"));
p("a_8".matches("w{3}"));
p("abc888&^%".matches("[a-z]{1,3}d+[&^#%]+"));
p("".matches("\"));
//边界处理
p("hello sir".matches("^h.*"));
p("hello sir".matches(".*ir$"));
p("hello sir".matches("^h[a-z]{1,3}ob.*"));
p("hellosir".matches("^h[a-z]{1,3}ob.*"));
//匹配空白行
p(" n".matches("[s&&[^n]]*n$")); */
// p("asdfasdfsafsf@dsdfsdf.com".matches("[w[.-]]+@[w[.-]]+.[w]+"));
// p("swrite@qq.com".matches("[w[.-]]+@[w[.-]]+.[w]+"));
// Pattern p = Pattern.compile("d{3,5}");
// String s = "123-34345-234-00";
// Matcher m = p.matcher(s);
// p(m.matches());
// p(m.reset());
// p(m.find());
// p(m.start()+"-"+m.end());
// p(m.find());
// p(m.start()+"-"+m.end());
// p(m.find());
// p(m.start()+"-"+m.end());
// p(m.find());
// p(m.lookingAt());
// p(m.lookingAt());
// p(m.lookingAt());
// p(m.lookingAt());
/* 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+=1;
if(i%2==0){
m.appendReplacement(buf,"java");
} else{
m.appendReplacement(buf,"JAVA");
}
}
m.appendTail(buf);
p(buf);*/
// Pattern p=Pattern.compile("(d{3,5})([a-z]{2})");
//// Pattern p=Pattern.compile("(d{3,5})([a-z]{2})");
// String s = "123aa-34345bb-234cc-00";
// Matcher m=p.matcher(s);
// while(m.find()){
// p(m.group(1));
// }
/* Pattern p=Pattern.compile(".{3,10}[0-9]"); //一口全部吞进去，然后不合适在一个一个吐，例如：一下子把aaaa1bbbb2 吞进去
Pattern p2=Pattern.compile(".{3,10}?[0-9]"); //一小口一小口吞，首先吞3个字母，然后后面的不匹配接着找数字
Pattern p3=Pattern.compile(".{3,10}+[0-9]"); //一口吞进去了就不吐了
String test="aaaa1bbbb2";
String test_3="aaaa1bbbb21";
Matcher m=p.matcher(test);
Matcher m2=p2.matcher(test);
Matcher m3=p3.matcher(test);
Matcher m3_1=p3.matcher(test_3);
if(m.find()){
System.out.println(m.start()+"-"+m.end());
}
if(m2.find()){
System.out.println(m2.start()+"-"+m2.end());
}
if(m3.find()){
System.out.println(m3.start()+"-"+m3.end());
}else{
p("not found");
}if(m3_1.find()){
System.out.println(m3_1.start()+"-"+m3_1.end());
}else{
p("not found");
}
*/
/* Pattern p=Pattern.compile(".{3}a$");
String a="abca";
Matcher m=p.matcher(a);
while(m.find()){
p(m.group());
}*/
Pattern p=Pattern.compile(".{3}(?=a)");//前面跟着3个字母，且是以a 结束的，但是不包括a
String a="44a66b";
Matcher m=p.matcher(a);
while(m.find()){
p(m.group());
}
Pattern p2=Pattern.compile("(?=a).{3}");//以a 为头，输入三个字母，若符合条件就捕获abc
String a2="44a66b";
Matcher m2=p2.matcher(a2);
while(m2.find()){
p(m2.group());
}
Pattern p3=Pattern.compile("(?!a).{3}");//前面不能是a
String a3="44a66b";
Matcher m3=p2.matcher(a3);
while(m3.find()){
p(m3.group());
}
Pattern p4=Pattern.compile(".{3}(?!a)");//后面跟着的不能是a
String a4="44a66b";
Matcher m4=p2.matcher(a4);
while(m4.find()){
p(m4.group());
}
Pattern p5=Pattern.compile(".{3}(?<!a)");//从后面往前读， 不能是a 的 ||.{3}(?<=a) 是a d的，则输出44a,a66 . 若写在前面则不算进去a,写在后则算进去a
String a5="44a66b";
Matcher m5=p2.matcher(a5);
while(m5.find()){
p(m5.group());
}
Pattern p6=Pattern.compile(".{3}(?<=a)");//后面跟着的不能是a
String a6="44a66b";
Matcher m6=p2.matcher(a6);
while(m6.find()){
p(m6.group());
}
Pattern px = Pattern.compile("(d(d))2"); //指 找到第一组12 两个数字之后，后面的再一组还必须和第一组一样
String s = "122";
Matcher mx = p.matcher(s);
p(mx.matches());
Pattern pa = Pattern.compile("java",Pattern.CASE_INSENSITIVE);
p("Java".matches("(?i)(java)"));// 上面方法的简写
}
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