用正则表达式提取区号

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Main {
	public static void main(String[] args) {
		System.out.println(isNumber("1001-5226656555"));
	}

	public static String isNumber(String s) {// 提取一个区号
		String regex = "^(\\d{1,4})\\-(\\d{5,})$";
		Pattern p = Pattern.compile(regex);
		Matcher m = p.matcher(s);
		if (m.matches()) {
			return m.group(1);
		}
		return null;
	}
}

结果：1001