正则表达式--实例

 实例1：可能以一个负号开头，并且后面跟着一位或者多位数字

System.out.println("-1233".matches("-?\\d+"));
System.out.println("1233".matches("-?\\d+"));
System.out.println("+1233".matches("-?\\d+"));
//竖直线表示或操作，因为加号有特殊意义，所以通过\\进行转义俄日普通字符。
System.out.println("+1233".matches("(-|\\+)?\\d+"));

运行结果：

true
true
false
true

实例2：\W表示非单词字符        \w表示一个单词字符   n\\W+:字母n后面跟着一个或者多个非单词字符  

String spress = "Spare time determines one's achievements.";
//以非单词字符分割
System.out.println(Arrays.toString(spress.split("\\W+")));
System.out.println(spress.replaceFirst("one'\\w+", "the possessive form of one"));
System.out.println(spress.replaceAll("time|one", "times"));

运行结果：

[Spare, time, determines, one, s, achievements]
Spare time determines the possessive form of one achievements.
Spare times determines times's achievements.

实例3：匹配时间   ^(0?[0-9]|1[012]):[0-5][0-9]\s*[ap]m$

实例4，简单的爬虫

package net.sunniwell.regular;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class SwRegularTest {

	public static void main(String[] args) {
		String urlContent = getUrlContent();
		// <a href="http://tuijian.hao123.com/games"
		doUrlRegular(urlContent,"href=\\\"([\\\\w\\\\s.:/]+?)\\\"");
	}

	private static void doUrlRegular(String urlContent,String regularStr) {
		Pattern pattern = Pattern.compile(regularStr);
		Matcher matcher = pattern.matcher(urlContent);
		while (matcher.find()) {
			System.out.println(matcher.group(1));
		}
	}

	private static String getUrlContent() {
		StringBuffer stringBuffer = new StringBuffer();
		try {
			URL url = new URL("http://www.hao123.com");
			BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(url.openStream()));
			String temp = "";
			while ((temp = bufferedReader.readLine()) != null) {
				stringBuffer.append(temp);
			}
		} catch (MalformedURLException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return stringBuffer.toString();
	}

}

实例5：判断数字在（0-20]，可以有2为小数的，但不能以0开头的整数

正则表达式：^(((1\d|[1-9])(\.\d{1,2})?)|(0(\.\d{1,2})))$  尽自己能力写了，不过觉得有点繁琐，以后知识积累后再优化。

上面有个bug,不能去除0.00 ，网友提供了一个^(?!0(\.0+)?$)1?[0-9](\.[0-9]{1,2})?$，挺好使的。