Java中Pattern.compile函数的使用详解

import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class ReFlags {
 public static void main(String[] args) {  
  Pattern p=Pattern.compile("^java",Pattern.CASE_INSENSITIVE|Pattern.MULTILINE);
  /*
   * 使用Pattern.CASE_INSENSITIVE（大小写不敏感的匹配）和Pattern.MULTILINE（多行模式）标记，忽略大小写地匹配所有以java开头的行
   */
  
  Matcher m=p.matcher("java has regex\nJava has regex\n"
    + "JAVA has pretty good regular expression\n"
    + "Regular expressions are in JavA");
  while (m.find()) { 
   System.out.println(m.group());//输出已匹配的部分  
  }
 }
}

import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class ReFlags_Comments {
 public static void main(String[] args) {
  /*
   * 不使用Pattern.COMMENTS(不启动注释)
   */
         String s="123";
         Pattern p1=Pattern.compile(" (\\d+)+#test comments");
         Matcher m1=p1.matcher(s);
         System.out.println(m1.matches());//false
         /*
                    * 正则表达式中使用启动注释的标记
          */
         Pattern p2=Pattern.compile("(?x) (\\d+)+#test comments");
         Matcher m2=p2.matcher(s);
         System.out.println(m2.matches());//true
         /*
               * 参数中使用Pattern.COMMENTS以启动注释
          */
         Pattern p3=Pattern.compile("  (\\d+)+#test comments",Pattern.COMMENTS);
         Matcher m3=p3.matcher(s);
         System.out.println(m3.matches());//true 
 }
}

Pattern Pattern.compile(String regex, int flag)