孟岩写了一篇文章说 正则表达式 ,我试了一下java的，见 Java Tutorial

1.Greedy

2.Reluctant

3.Possessive

先看个例子：

while (matcher.find()) {
                console.format(”I found the text /”%s/” starting at ” +
                   “index %d and ending at index %d.%n”,
                    matcher.group(), matcher.start(), matcher.end());
                found = true;
            }

比如说字符串是“<book> <title> Perl Hacks </title> </book>/t”

那么pattern是

1。”<.*>”,则结果是：I found the text “<book> <title> Perl Hacks </title> </book>” starting at index 0 and ending at index 42.

2。”<.*?>”,则结果是：

I found the text “<book>” starting at index 0 and ending at index 6.
I found the text “<title>” starting at index 7 and ending at index 14.
I found the text “</title>” starting at index 26 and ending at index 34.
I found the text “</book>” starting at index 35 and ending at index 42.

3。”<.*+>”,那么就什么也找不到

greedy：吃掉整个字符串，看是否match，如果不配，则backtracking吐出一个个字符，看是否匹配

reluctant：也就是我们说的lazy，过程相反，从字符串开始，一个个字符看是否匹配，最后做的是整个字符串

possessive:吃掉整个字符串，但是不往外吐，结果是没找到（作用是??)，做一次且一次