关于一个奇怪的Java正则表达式行为的问题

"^[\\.\\d]+"

下面是我的代码:

public void testMiscellaneous() throws Exception {
    System.out.println("~~~~~~~~~~~~~~~~~~~testMiscellaneous~~~~~~~~~~~~~~~~~~~~");
    String s1 = ".123 *[DP7_Dog]";
    String s2 = ".123";
    String s3 = "1.12.3";
    String s4 = "a1.12.3";
    final String numberRegex = "^[\\.\\d]+";
    System.out.println(s1.matches(numberRegex));
    System.out.println(s2.matches(numberRegex));
    System.out.println(s3.matches(numberRegex));
    System.out.println(s4.matches(numberRegex));
}

输出为

false
true
true
false