微妙的Java正则表达式

String str = "1234545";
String regex = "\\d*";

Pattern p1 = Pattern.compile(regex);
Matcher m1 = p1.matcher(str);

while (m1.find()) {

    System.out.print(m1.group() + " found at index : ");
    System.out.print(m1.start());

}

该程序的输出为 1234545 found at index:0 found at index:7 .

我的问题是:
为什么打印了一个空格,而实际上在 str .