本文将介绍Java正则表达式中的Pattern类与Matcher类。首先我们要清楚指定为字符串的正则表达式必须首先被编译为pattern类的实例。因此如何更好的了解这两个类，是编程人员必须知道的。

Pattern p = Pattern.compile("a*b");
Matcher m = p.matcher("aaaaab");
boolean b = m.matches(); 

  1 import java.util.regex.Matcher;
  2 import java.util.regex.Pattern;
  3 /**
  4  * java中运用正则表达式的两个重要类:Pattern与Matcher
  5  * @author fhd001
  6  */
  7 public class PatternAndMatcherTest {
  8      public static void main(String[] args) {
  9         /*
 10          * 常用的调用
 11          */
 12         Pattern p1 = Pattern.compile("a*b");
 13         String str1 = "aaaab";
 14         Matcher m1 = p1.matcher(str1);
 15         boolean b1 = m1.matches();
 16         System.out.println(b1);
 17
 18         String str2 = "b";
 19         Matcher m2 = p1.matcher(str2);
 20         boolean b2 = m2.matches();
 21         System.out.println(b2);
 22          /*
 23          * 另一种调用
 24          * 等效于上面的语句，尽管对于重复的匹配而言它效率不高，因为它不允许重用已编译的模式。
 25          * 但它可供多个并发线程安全使用,而上面的调用则就不是安全的.
 26          */
 27         boolean b3 = Pattern.matches("a*b", "aaab");
 28         System.out.println(b3);
 29
 30         //Pattern类的pattern方法:从pattern类的实例中返回匹配模式的字符串表示
 31         String pattern1 = p1.pattern();
 32         System.out.println(pattern1);
 33
 34         //Pattern类的split方法
 35         String[]arr1 = p1.split("rrrrraaabccccaaaaab");
 36         for (String string : arr1) {
 37             System.out.println(string+">>>>");
 38         }
 39         /*
 40          * Matcher类
 41          *
 42          * matches方法:       方法尝试将整个输入序列与该模式匹配
 43          * lookingAt方法: 尝试将输入序列从头开始与该模式匹配,与 matches 方法类似，
 44          *                  此方法始终从区域的开头开始；与之不同的是，它不需要匹配整个区域。
 45          * find方法:          方法扫描输入序列以查找与该模式匹配的下一个子序列
 46          */
 47         String str3 = "aabbcccaaaaaeeeaaaaaaaaagggga";
 48         Pattern p3 = Pattern.compile("a+");
 49         Matcher m3 = p3.matcher(str3);
 50         boolean bo4 = m3.matches();
 51         System.out.println("matches方法:  "+bo4);
 52         /*
 53          * lookingAt方法,从开头第一个字符进行匹配,匹配成功了不再继续匹配,
 54          * 从第一个字符开始,匹配失败了,也不继续匹配.不需要匹配整个序列
 55          */
 56         boolean bo5 = m3.lookingAt();
 57         if(bo5){
 58             //group方法(不带参数)返回的就是匹配的子字符串.
 59             System.out.println("lookingAt方法:  "+m3.group());
 60         }
 61      //find方法:找到一个匹配的子串,还会继续找下一个子串.
 62         while(m3.find()){
 63             System.out.println("find方法:  "+m3.group());
 64         }
 65      /*
 66          * 带参数的group方法与不带参数的group方法区别
 67          * 不带参数的group方法:find方法与lookingAt方法匹配出来的子序列(上面有演示)
 68          * 带参数的group方法: 返回在以前匹配操作期间由给定组捕获的输入子序列。
 69          */
 70         String str6 = "aaabbbccc";
 71         Pattern p5 = Pattern.compile("(a+)(b+)(c+)");
 72         Matcher m5 = p5.matcher(str6);
 73         boolean boo = m5.matches();
 74         if(boo){
 75             int k = m5.groupCount()+1;//加1就是把0下标的整个字符序列加上,它也作为一组放在0下标的位置.
 76             if(k>0){
 77                 for(int i=0;i                    System.out.println(m5.group(i));
 78                 }
 79             }
 80         }
 81     }
 82 }

true
true
true
a*b
rrrrr>>>>
cccc>>>>
matches方法:  false
lookingAt方法:  aa
find方法:  aaaaa
find方法:  aaaaaaaaa
find方法:  a
aaabbbccc
aaa
bbb
ccc 

 1 import java.io.BufferedReader;
 2 import java.io.FileInputStream;
 3 import java.io.FileOutputStream;
 4 import java.io.IOException;
 5 import java.io.InputStream;
 6 import java.io.InputStreamReader;
 7 import java.io.OutputStream;
 8 import java.util.regex.Matcher;
 9 import java.util.regex.Pattern;
10
11 public class PatternTest {
12     public static void main(String[] args) {
13         try {
14             replaceInFile("<name>.*</name>","C:\\project.xml","<name>BigDataDemo</name>");
15         } catch (IOException e) {
16             e.printStackTrace();
17         }
18
19     }
20     public static void replaceInFile(String regex, String fileName, String replacement) throws IOException {
21         InputStream in = new FileInputStream(fileName);
22         StringBuffer buffer = new StringBuffer();
23         try {
24             Pattern p = Pattern.compile(regex);
25             InputStreamReader inR = new InputStreamReader(in);
26             BufferedReader buf = new BufferedReader(inR);
27             String line;
28             while ((line = buf.readLine()) != null) {
29                 Matcher matcher = p.matcher(line);
30                 if (matcher.find()) {
31                     line = matcher.replaceAll(replacement);
32                 }
33                 buffer.append(line).append("\n"); //$NON-NLS-1$
34             }
35         } catch (IOException e) {
36             //
37         } finally {
38             in.close();
39         }
40
41         OutputStream os = new FileOutputStream(fileName);
42         os.write(buffer.toString().getBytes());
43         os.close();
44     }
45 }

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <projectDescription>
 3     <name>BigDataDemo</name>
 4     <comment>
 5 To have ready-to-use Job Designs at your disposal, import the Demo Project include in Talend Open Studio.
 6
 7 Simply follow the steps below:
 8
 9     * Launch Talend Open Studio
10     * In the login window, click on Demo
11     * Choose Java or Perl Demo Project
12     * Click on Finish to complete the operation
13     * Choose the TALENDDEMOJAVA or TALENDDEMOPERL on the &quot;Existing&quot; list
14     * Click on Ok</comment>
15     <projects>
16     </projects>
17     <buildSpec>
18     </buildSpec>
19     <natures>
20         <nature>org.talend.core.talendnature</nature>
21     </natures>
22 </projectDescription>