android studio screen orientation Save

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Very easily android Application screen orientation Save. 
First watch the video.

Step 1 Java Class Save

package com.example.screen_orientation_save;

import android.app.Application;
;

public class Save extends Application{
    private int i =0;
    int ap(){
        return i++;
    }
}

Step 2 AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.screen_orientation_save">

    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.INTERNET"/>
    <application
        android:name=".Save"
        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=".Screen_1_Youtube_Activity"
            android:configChanges="orientation|screenSize|keyboardHidden"/>
        <activity android:name=".Screen_3_Google_Activity"
            android:configChanges="orientation|screenSize|keyboardHidden"/>
        <activity android:name=".Screen_1_Facebook_Activity"
            android:configChanges="orientation|screenSize|keyboardHidden"/>
        <activity
            android:name=".MainActivity"
            android:configChanges="orientation|screenSize|keyboardHidden">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>