Java 无法通过android studio在android应用程序中创建文件夹

Iam正在外部存储目录中创建文件夹。我已在android清单中添加了所有权限

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.myapplication">
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"> 
</uses-permission>
<uses-permission android:name="android.permission.READ_INTERNAL_STORAGE" > 
</uses-permission>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" > 
</uses-permission>
<uses-permission android:name="android.permission.WRITE_INTERNAL_STORAGE" > 
</uses-permission>
<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">

    <activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

</manifest>

getExternalStorageDirectory（）返回/storage/emulated/0。请告诉我如何创建此文件夹。请忽略任何语法错误

 try {
        File root = new File(Environment.getExternalStorageDirectory(), 
 "Notes");
        
 Toast.makeText(this,Environment.getExternalStorageDirectory().toString() , 
 Toast.LENGTH_SHORT).show();
        if (!root.exists()) {
            Toast.makeText(this, "Directory does not exist", 
Toast.LENGTH_SHORT).show();
            root.mkdirs();
        }