正则表达式的应用

当我们要处理一条长长的字符对象是，我们可以用Pattern类或者String内带的一些有用的正则表达式方法。
String含有正则表达式常用方法：split(),replace(),replaceAll(),matches()等等。
代码例子：

public class Test
{
    public static void main(String[] args)
    {
        //要匹配的字符
        String s="<div class="sTitle">可能存在类似的问题</div><div class="sFooter"><a class="sFirstNewAsk">我想提一个新问题</a></div>";
        //匹配中文的正则表达式 
        String rege="[u4e00-u9fa5]+";         
        //获得HTML的标签和属性
        System.out.println(Arrays.toString(s.split(rege)));
        //替换第一段中文内容
        System.out.println(s.replaceFirst(rege,"beyondboy"));
        //替换所有的中文内容
        System.out.println(s.replaceAll(rege,"scau"));
        //只判断开头是否含有中文内容
        System.out.println(s.matches(rege));
    }
}

运行结果：
[<div class="sTitle">,</div><div class="sFooter"><a class="sFirstNewAsk">,</a></div>]
<div class="sTitle">beyondboy</div><div class="sFooter"><a class="sFirstNewAsk">我想提一个新问题</a></div>
<div class="sTitle">scau</div><div class="sFooter"><a class="sFirstNewAsk">scau</a></div>
false
面对一些复杂的文本内容处理我们可以结合Pattern和Matcher来使用，常用方法：find(),group(),start(),end(),matches(),lookingAt(),appendReplacement(),appendTail(),reset()等等。
代码例子：

public class Test
{
    public static void main(String[] args)
    {
        //要匹配的字符
        String s="58.27.82.161@02/10/2005n" +
                "204.45.234.40@02/11/2005n" +
                "58.27.82.161@02/11/2005n" +
                "58.27.82.161@02/12/2005n" +
                "58.27.82.161@02/12/2005n" +
                "[Next log section with different data format]";
        //匹配邮箱的正则表达式 
        String regex="(d+[.]){3}d+@(d{2}/){2}d+";       
        Pattern pattern=Pattern.compile(regex);
        System.out.println(pattern.split(regex));
        //获得该matcher对象
        Matcher matcher=pattern.matcher(s);
        while (matcher.find())
        {
            //获得与(d+[.]){3}d+@(d{2}/){2}d+匹配的内容
            System.out.println("matcher.groud():"+matcher.group()+ "" at positions " +
                      matcher.start() + "-" + (matcher.end() - 1));     
            //获得与(d+[.])匹配的内容
            System.out.println("matcher.groud(1):"+matcher.group(1));
            //获得与(d{2}/)匹配的内容
            System.out.println("matcher.groud(2):"+matcher.group(2));       
        }
        //下面是比较matches()和lookingAt()区别
        Matcher matcher2=test("beyondboy from scau","w+yond");
        //lookingAt()只要前面第一部分匹配就会成功
        System.out.println(matcher2.lookingAt());
        //matches()只有整个字符内容匹配才能成功
        System.out.println(matcher2.matches());
        matcher2=test("beyondboy from scau",".*yond.*");
        System.out.println(matcher2.lookingAt());
        System.out.println(matcher2.matches());
        //appendReplacement()和appendTail()方法的使用
        Matcher matcher3=test("12345789123456987654","345");
        StringBuffer buffer=new StringBuffer();
        while (matcher3.find())
        {
            //添加匹配的前面部分的内容
            matcher3.appendReplacement(buffer,"4");
            System.out.println("matcher3.appendReplacement():"+buffer);
            //添加没有匹配剩下的内容
            matcher3.appendTail(buffer);
            System.out.println("matcher3.appendTail():"+buffer);
        }
        buffer.setLength(0);
        matcher3.reset();
        //这两种方法一般是这样结合用的
        while(matcher3.find())
            matcher3.appendReplacement(buffer,"4");
        matcher3.appendTail(buffer);
        System.out.println("matcher3.appendTail():"+buffer);
    }   
    private static Matcher test(String s,String regex)
    {
        Pattern pattern=Pattern.compile(regex);
        Matcher matcher=pattern.matcher(s);
        return matcher;
    }
}

运行结果：
[Ljava.lang.String;@d0da1d8
matcher.groud():58.27.82.161@02/10/2005” at positions 0-22
matcher.groud(1):82.
matcher.groud(2):10/
matcher.groud():204.45.234.40@02/11/2005” at positions 24-47
matcher.groud(1):234.
matcher.groud(2):11/
matcher.groud():58.27.82.161@02/11/2005” at positions 49-71
matcher.groud(1):82.
matcher.groud(2):11/
matcher.groud():58.27.82.161@02/12/2005” at positions 73-95
matcher.groud(1):82.
matcher.groud(2):12/
matcher.groud():58.27.82.161@02/12/2005” at positions 97-119
matcher.groud(1):82.
matcher.groud(2):12/
true
false
true
true
matcher3.appendReplacement():124
matcher3.appendTail():124789123456987654
matcher3.appendReplacement():124789123456987654789124
matcher3.appendTail():1247891234569876547891246987654
matcher3.appendTail():1247891246987654
Scanner类也可以用正则来控制内容输出，常用方法hasNext(),useDelimiter(),next()方法。
代码例子：

public class Test
{
    public static void main(String[] args)
    {
        //要匹配的字符
        String s="<<<beyondboy>>>>> from >>scau ";
        Scanner scanner=new Scanner(s);
        scanner.useDelimiter("(<* *>* *)");
        //获得英语字符
        while(scanner.hasNext())
        {
            System.out.println(scanner.next());
        }
        //要匹配的字符
        String threatData =
                "58.27.82.161@02/10/2005n" +
                "204.45.234.40@02/11/2005n" +
                "58.27.82.161@02/11/2005n" +
                "58.27.82.161@02/12/2005n" +
                "58.27.82.161@02/12/2005n" +
                "[Next log section with different data format]";
         String pattern = "(d+[.]d+[.]d+[.]d+)@" +
                  "(d{2}/d{2}/d{4})";
        Scanner scanner2=new Scanner(threatData);
        while(scanner2.hasNext(pattern))
        {
            //获得匹配的内容
            System.out.println(scanner2.next(pattern));
             MatchResult match = scanner2.match();
              String ip = match.group(1);
              String date = match.group(2);
              //分别输出(d{2}/d{2}/d{4})，(d+[.]d+[.]d+[.]d+)的内容
              System.out.format("Threat on %s from %sn",date,ip);
        }
    }   
}

运行结果： b e y o n d b o y f r o m s c a u 58.27.82.161@02/10/2005 Threat on 02/10/2005 from 58.27.82.161 204.45.234.40@02/11/2005 Threat on 02/11/2005 from 204.45.234.40 58.27.82.161@02/11/2005 Threat on 02/11/2005 from 58.27.82.161 58.27.82.161@02/12/2005 Threat on 02/12/2005 from 58.27.82.161 58.27.82.161@02/12/2005 Threat on 02/12/2005 from 58.27.82.161