正则表达式的贪婪，勉勉强强，独占模式[转]

正则表达式的贪婪，勉强，独占模式[转]

public static void main(String[] args) {String s = "xxyyxxxyxxyxx";Pattern greedy = Pattern.compile("xx(.*)xx");Pattern reluctant = Pattern.compile("xx(.*?)xx");Pattern possessive = Pattern.compile("xx(.*+)xx");Matcher m1 = greedy.matcher(s); Matcher m2 = reluctant.matcher(s); Matcher m3 = possessive.matcher(s); while(m1.find()) {System.out.println("greedy..." + m1.group(1));}while(m2.find()) {System.out.println("reluctant..." + m2.group(1));}while(m3.find()) {System.out.println("possessive..." + m3.group(1));}}

输出结果
greedy...yyxxxyxxy
reluctant...yy
reluctant...y

greedy (.*)吃掉整字符串，然后从最后一个字符开始回退，所以找到最后一个xx
reluctant (.*?)从左侧开始匹配最少的字符，每当找到一个xx结尾就匹配一次
possessive (.*+)因为吃掉整个字符串后面没有xx，而且不会进行回退，所以没有匹配到任何结果

一个用于替换字符串模式的例子：

public class StringAnalysis {/** * 将字符串中特定模式的字符转换成map中对应的值 *  * @param s *            需要转换的字符串 * @param map *            转换所需的键值对集合 * @return 转换后的字符串 */public static String convert(String s, Map<String, String> map) {Matcher m = Pattern.compile("<#=(.*?)#>").matcher(s);StringBuffer sb = new StringBuffer();while (m.find()) {String value = map.get(m.group(1));m.appendReplacement(sb, value != null ? value : "null");}m.appendTail(sb);return sb.toString();}public static void main(String[] args) {String str = "姓名:<#=name#>\n性别:<#=sex#>\n住址:<#=address#>\n联系方式:<#=linkinf#>";Map<String, String> map = new HashMap<String, String>();map.put("xxx", "哈哈");map.put("name", "Steven");map.put("address", "XX市XX区XXX二路X-X号X室");map.put("linkinf", "13577777777");System.out.println(convert(str, map));}}

输出结果：
姓名:Steven
性别:null
住址:XX市XX区XXX二路X-X号X室
联系方式:13577777777

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