严重错误：1：1：序言中不允许包含内容。org.xml.sax.SAXParseException

我正在尝试读取Java中的XML文件，然后将其与其XML Schema进行比较，但我无法克服此错误：

[致命错误]：1：1：序言中不允许包含内容。org.xml.sax.SAXParseException; lineNumber：1；columnNumber：1；序言中不能有内容。

这是文件读取的开始

try {
        DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
        DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();          
        Document doc = dBuilder.parse(new InputSource(new StringReader("myfile.xml"))); // ERROR OCCURS HERE

我通过HEX编辑器扫描了XML，但是内部没有发现任何奇怪的字符，因此我不知道问题出在哪里

myfile.xml

<?xml version="1.0" encoding="UTF-8" standalone="no"?>

<Schedule xmlns ="schedule"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:noNamespaceSchemaLocation="schedule.xsd">
    <Lesson>
        <Title>Artificial Intelligence</Title>
        <Lecture Classroom="BA">
            <Day>Wednesday</Day>
            <Time>09-11</Time>
        </Lecture>
        <Professor>Hatzilygeroudis</Professor>
    </Lesson>
    <Lesson>
        <Title>Constraint Satisfaction Problems</Title>
        <Lecture Classroom="B3">
            <Day>Monday</Day>
            <Time>19-21</Time>
        </Lecture>
    </Lesson>
    <Lesson>
        <Title>Knowledge Representation in Web</Title>
        <Lecture Classroom="P200">
            <Day>Friday</Day>
            <Time>15-17</Time>
        </Lecture>
        <Professor>Hatzilygeroudis</Professor>
    </Lesson>
    <Lesson>
        <Title>Artificial Intelligence</Title>
        <Lecture>
            <Day>Monday</Day>
            <Time>19-21</Time>
        </Lecture>
    </Lesson>
    <Lesson>
        <Title>AI Programming</Title>
        <Lecture Classroom="B3">
            <Day>Monday</Day>
            <Time>11-13</Time>
        </Lecture>
    </Lesson>
    <Lesson>
        <Title>Introduction to Procedural Programming</Title>
        <Lecture Classroom="P200">
            <Day>Wednesday</Day>
            <Time>15-17</Time>
        </Lecture>
        <Professor>Papadopoulos</Professor>
    </Lesson>
</Schedule>