System.out.println(s.split(" ")[1]);或者System.out.println(s.split("\\s")[1]);

System.out.println(s.split("\\s+")[1]);

int begin = s.indexOf(" ");
int end = s.indexOf(" ", begin+1);
System.out.println(s.substring(begin+1, end));

public class RegExp {
 
  public boolean match(String reg, String str) {
    return Pattern.matches(reg, str);
  }
 
  public List<String> find(String reg, String str) {
    Matcher matcher = Pattern.compile(reg).matcher(str);
    List<String> list = new ArrayList<String>();
    while (matcher.find()) {
      list.add(matcher.group());
    }
    return list;
  }
   
  public String find(String reg, String str, int index) {
    Matcher matcher = Pattern.compile(reg).matcher(str);
    if (matcher.find()) {
      return matcher.group(index);
    }
    return null;
  }
 
  public String findString(String reg, String str) {
    String returnStr = null;
    List<String> list = this.find(reg, str);
    if (list.size() != 0)
      returnStr = list.get(0);
    return returnStr;
  }
 
}

 RegExp re = new RegExp();
 System.out.println(re.findString("\\d+", s));

 System.out.println(re.findString("(?<=共).*?\\d+", s).trim());

System.out.println(s.replaceFirst(".*?(\\d+).*", "$1"));