JAVA正则表达式笔记

JAVA 正则表达式涉及的三个类:
String,Pattern,Matcher
Pattern是要匹配的模式,Matcher是匹配的结果.

例如:Pattern p = Pattern.complie("[a-z]{3}");
     Matcher m = p.mather("abc");
要想在正则表达式中匹配一个反斜线用四个反斜线表示: " \\".matches("\\\\");
匹配空白行 " \n".matches("^[\\s&&[^\\n]]*\\n$");

找出匹配结果在整个字符串的开始位置和结束位置
Pattern p = Pattern.complie(" \\d{3,5}");
String a = "123-2135-155-00";
Matcher m = p.matcher(s);
m.matches() // 匹配整个字符串,因此这里是false;
m.reset();
while(m.find()) // 找一个和这个模式所匹配的子串
{
        System.out.println(m.start() + "To" + m.end());
}
将匹配到的java都转换成大写的
Pattern p = Pattern.complie("java", Pattern.CASE_INSENSITIVE);
Matcher m = p.matcher("java Java JaVa IloveJava You HateJaVA");
m.replaceAll("JAVA");

将匹配偶数个转换为大写,奇数个转换为小写
package zx.test;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class TestPattern
{
       
        public static void main(String[] args)
        {
               
                StringBuffer newString = new StringBuffer();
                String isPatternString = "java Java JaVa IloveJava You HateJaVA";
                Pattern p = Pattern.compile("java", Pattern.CASE_INSENSITIVE);
                Matcher m = p.matcher(isPatternString);
               
                int i = 0;
                while(m.find())
                {
                        i++;
                        if (i % 2 == 0)
                        {
                                m.appendReplacement(newString, "java");
                        }
                        else
                        {
                                m.appendReplacement(newString, "JAVA");
                        }
               
                }
                m.appendTail(newString);
               
                System.out.println(newString);
        }
}

输出结果:JAVA java JAVA Ilovejava You HateJAVA

Java正则表达式分组:
        private static void testGroup()
        {
                String s = "3412afdsaf-34ijii-422342k23-423423fsdfaf";
                Pattern p = Pattern.compile("( \\d{1,10})([a-z]{1,9})"); // 组1:( \\d{1,10}) 组2:([a-z]{1,9})                 Matcher m = p.matcher(s);                                 while(m.find())                 {                         System.out.println("Group0: " + m.group() + " Group1: " + m.group(1) + " Group2: " + m.group(2));                 }         } 输出结果: Group0: 3412afdsaf Group1: 3412 Group2: afdsaf Group0: 34ijii Group1: 34 Group2: ijii Group0: 422342k Group1: 422342 Group2: k Group0: 423423fsdfaf Group1: 423423 Group2: fsdfaf