java 正则匹配开头和结尾字符串，中间为固定个数的字符

public class TestDemo {

	public static void main(String[] args) {
		//匹配以∈{开头，中间7个字符 ，以}∈结尾的字符串 
		boolean isMatch1 = Pattern.matches("^∈\\{+.{7}\\}∈$", "∈{ddddddd}∈");
		System.out.println(isMatch1);

		boolean isMatch = Pattern.matches("^∞+.{7}∞$", "∞ddddddd∞");

		// .为任意字符串， "^∞+\\d{7}∞$" 表示中间7位字符必须为数字
		Pattern p = Pattern.compile("^∞+.{7}∞$");
		Matcher matcher = p.matcher("∞1212a21∞");
		System.out.println(matcher.find());
	}

}