java正则 提取两个字符串中间的字段

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

public class Cat
{
	public static void main(String[] args)
	{
		String str = "asdf_{asd}_fas_{dfa}_sdfasdf_{dfa}_ ";
		String reg = "_\\{((?:(?!\\}_)[\\s\\S])*)\\}_";
		Pattern pattern = Pattern.compile(reg);
		Matcher matcher = pattern.matcher(str);
		while(matcher.find())
		{
			System.out.println(matcher.group(1));
		}
	}
}

Pattern pattern = Pattern.compile("_\\{(.*?)\\}_");
Matcher matcher = pattern.matcher("asdf_{asd}_fas_{dfa}_sdfasdf_{dfa}_");
while(matcher.find()){
    System.out.println(matcher.group(1));
}