I want to print a varValue of an object with it's related review objects.

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• Android PDF Viewer null object reference error

  I am using barteksc Android PDF Viewer like many others (https://github.com/barteksc/AndroidPdfViewer). I keep receiving a null object reference error. This is the error.

  E/AndroidRuntime: FATAL EXCEPTION: main
                    Process: group6.interactivehandwriting, PID: 24037
                    java.lang.RuntimeException: Unable to start activity ComponentInfo{group6.interactivehandwriting/group6.interactivehandwriting.activities.RoomActivity.RoomActivity}: android.view.InflateException: Binary XML file line #9: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
  

  I have checked to make sure I am referencing the views correctly. The asset I am loading called "sample.pdf" is in my assets.

  * Can you see any reason why I am receiving this error? *

  I realize there are multiple post about this library, however every instance seems to be unique so I decided to go ahead and ask.

  RoomActivity.java

  package group6.interactivehandwriting.activities.RoomActivity;
  
  import android.content.res.AssetManager;
  import android.os.Bundle;
  import android.app.Activity;
  import android.util.Log;
  import android.view.View;
  
  import com.github.barteksc.pdfviewer.PDFView;
  import com.github.barteksc.pdfviewer.listener.OnLoadCompleteListener;
  import com.github.barteksc.pdfviewer.listener.OnPageChangeListener;
  import com.github.barteksc.pdfviewer.scroll.DefaultScrollHandle;
  
  import group6.interactivehandwriting.R;
  import group6.interactivehandwriting.activities.RoomActivity.views.DocumentView;
  import group6.interactivehandwriting.activities.RoomActivity.views.RoomView;
  
  public class RoomActivity extends Activity implements OnPageChangeListener, OnLoadCompleteListener {
      RoomView roomView;
      DocumentView docView;
      PDFView pView;
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          Log.d("Android: ", "Setting content view to an instance of RoomView in: " + this.getClass().getName());
          setContentView(R.layout.activity_draw);
  
          System.out.println("Attempting to set ImageView..");
          pView = (PDFView) findViewById(R.id.pdfView);
          pView.fromAsset("sample.pdf").defaultPage(0)
                  .enableSwipe(true).swipeHorizontal(false).
                  onPageChange(this).enableAnnotationRendering(true).onLoad(this).scrollHandle(new DefaultScrollHandle(this)).load();
  
  
      }
  
      @Override
      public void onPageChanged(int page, int pageCount) {
          setTitle(String.format("%s %s / %s", "Sample", page + 1, pageCount));
      }
  
      @Override
      public void loadComplete(int nbPages) {
      }
  }
  

  AndroidManifest.xml

  <?xml version="1.0" encoding="utf-8"?>
  <manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="group6.interactivehandwriting">
  
      <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
      <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=".activities.RoomActivity.RoomActivity"
              android:label="@string/title_activity_menu"
              android:theme="@style/AppTheme.NoActionBar">
              <intent-filter>
                  <action android:name="android.intent.action.MAIN" />
  
                  <category android:name="android.intent.category.LAUNCHER" />
              </intent-filter>
          </activity>
      </application>
  
  </manifest>
  

  activity_draw.xml

  <?xml version="1.0" encoding="utf-8"?>
  <android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"
      xmlns:tools="http://schemas.android.com/tools"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      tools:context=".activities.RoomActivity.RoomActivity">
  
      <view
          android:id="@+id/room_view"
          id="@+id/view"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          app:layout_constraintBottom_toBottomOf="parent"
          app:layout_constraintEnd_toEndOf="parent"
          app:layout_constraintStart_toStartOf="parent"
          app:layout_constraintTop_toTopOf="parent" />
  
      <com.github.barteksc.pdfviewer.PDFView
          android:id="@+id/pdfView"
          android:layout_width="match_parent"
          android:layout_height="match_parent"/>
  
      <TextView
          android:id="@+id/textView"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_marginStart="8dp"
          android:layout_marginTop="8dp"
          android:text="@string/room"
          app:layout_constraintStart_toStartOf="parent"
          app:layout_constraintTop_toTopOf="parent" />
  
  </android.support.constraint.ConstraintLayout>
  

  Dependencies:

  compile 'com.github.barteksc:android-pdf-viewer:2.8.2'
  
  compile 'org.apache.commons:commons-collections4:4.1'
  
• Consider defining a bean named 'entityManagerFactory' in your configuration.3

  I'm just following some tutorial how to upload documents via spring. So while working on it i faced above issue. Since there are many questions related to same question i refer them and tried everything but none corrected m problem. In advance i don't need to add @Repository for my Repository interface and @EnableJpaRepositories in my Application class as i have use correct package sequence. For more reference refer https://dzone.com/articles/spring-spring-boot-and-component-scan. Please help me out.

  Application class

  @SpringBootApplication
  @ComponentScan("com.project.abhishek")
  public class DocumnetwebApplication {
  
  public static void main(String[] args) {
      SpringApplication.run(DocumnetwebApplication.class, args);
  }}
  

  Controller

  @Controller
  public class DocumentController {
  
  @Autowired
  private DocumentRepository documentRepo;
  
  @RequestMapping("/displayUpload")
  public String displayUpload() {
      return "documentUpload";
  }
  
  @RequestMapping(value="/upload", method=RequestMethod.POST )
  public String upload(@RequestParam("document")MultipartFile multiPartFile, @RequestParam("id")long id) {
  
      Document document = new Document(); 
      document.setId(id);
      document.setName(multiPartFile.getName());
      try {
          document.setData(multiPartFile.getBytes());
      } catch (IOException e) {
          e.printStackTrace();
      }
      documentRepo.save(document);
  
      return "documentUpload";
  }}
  

  Bean

  @Entity
  public class Document {
  
  @Id
  private long id;
  private String name;
  @Lob
  private byte[] data;
  //getters and setters}}
  

  Repository

  public interface DocumentRepository extends JpaRepository<Document, Long> {}
  

  Application properties file

  spring.datasource.url=jdbc:mysql://localhost:3306/mydb
  spring.datasource.username=root
  spring.datasource.password=test
  spring.jpa.properties.hibernate.id.new_generator_mappings=false
  spring.jpa.show-sql=true
  server.port=8083
  spring.mvc.view.prefix=/WEB-INF/jsps/
  spring.mvc.view.suffix=.jsp
  server.servlet.context-path= /documentweb
  

  pom file

  <dependencies>
      <dependency>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-data-jpa</artifactId>
      </dependency>
      <dependency>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-web</artifactId>
      </dependency>
  
      <dependency>
          <groupId>mysql</groupId>
          <artifactId>mysql-connector-java</artifactId>
          <scope>runtime</scope>
      </dependency>
      <dependency>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-starter-test</artifactId>
          <scope>test</scope>
      </dependency>
      <dependency>
          <groupId>org.apache.tomcat.embed</groupId>
          <artifactId>tomcat-embed-jasper</artifactId>
          <version>9.0.12</version>
          <scope>provided</scope>
  
      </dependency>
      <dependency>
          <groupId>javax.servlet</groupId>
          <artifactId>jstl</artifactId>
      </dependency>
  
  </dependencies>
  

  Package Structure

  com.project.abhishek---application class  
  com.project.abhishek.controller  
  com.project.abhishek.entity  
  com.project.abhishek.repository
  
• Trying to fit the settings activity in a fragment window - Android Studio

  I am working on an app and something troubles me, I want to create a settings activity in a fragment layout and the thing is that if I create a settings activity from the android studio's menu (this), there's no way that I can transform it into a fragment. I want to make it be this way (photo) .

  The thing is that when i change fragments, i use theFragment = new fragment_body();, where it is public class fragment_body extends Fragment, with its onCreateView of:

  public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
          return inflater.inflate(R.layout.view_settings, null);
      }
  

  where on the settings activity i don't have any of these things, i've tried multiple things but i don't know how to do it. Where the settings activity is: public class SettingsActivity extends PreferenceActivity. Please guide me of how to do this, Thanks in advance.
• Electricity Billing System for Home in OOPS

  I recently appeared for interview for code-pairing round and I was asked following question: Electricity Billing System for home“. The corresponding power usage of home appliances(Fan, AC, Fridge, Light) was given:

  Appliance | Per hour unit consumption
  Fan 4
  Light 2
  AC 10
  Fridge 8
  

  The slab chart was given as:

  Slab 1 - 0 to 1000 unit: INR Rs 20 per unit
  Slab 2 - 1001 to 3000 unit: INR Rs 30 per unit
  Slab 1 - 3001 to 6000 unit: INR Rs 40 per unit
  Slab 1 - 6001 and above unit: INR Rs 50 per unit
  

  Input:

  Appliance | CountOfAppliance | TotalUasgePerDayInHours
  Fan 2 4
  Light 1 4
  AC 1 12
  Fridge 1 5
  

  Output:

  200000 INR
  Units Per Day : (2*4*4 + 1*4*2 +1*12*10 + 1*5*8) = 200
  unitsPerMonth = 6000
  totalBill = 1000*20 + 2000*30 + 3000*30 + 3000*50 = 200000
  

  I had modeled the code using "Factory Design Pattern" for appliance. But my Code for Price Slab was something the interviewer was not happy with the hardcoding. Though I modified it by using Constants file for slabs but the interviewer was still expecting something better. Kindly let me know how it can be improved.

  My Code:

  IElectricComponent

  public interface IElectricComponent {
      public enum Unit{
             FAN(4), LIGHT(2), AC(10) , FRIDGE(8);
             private int value;
             private Unit(int value) {
                  this.value = value;
             }
             public int getValue(){
              return value;
             }
         }
      public int claculateUnitForSingleDay();
  }
  

  Fan

  public class Fan implements IElectricComponent{
  
      private int noOfComponents;
      private int perDayUsage;
      public Fan(int noOfComponents, int perDayUsage){
          this.noOfComponents=noOfComponents;
          this.perDayUsage=perDayUsage;               
      }
  
      public int claculateUnitForSingleDay(){
          return noOfComponents*perDayUsage*Unit.FAN.getValue();      
      }   
  }
  

  The same way for Fridge,Light and Ac

  Factory : ApplianceFactory

  public class ApplianceFactory {
  
          public static IElectricComponent getInstance(String appliance, int countOfAppliance ,int perDayUsage ){
  
              switch(appliance){
  
                  case ApplianceConstants.FAN:
                      return new Fan(countOfAppliance,perDayUsage);
  
                  case ApplianceConstants.LIGHT:
                      return new Light(countOfAppliance,perDayUsage);
  
                  case ApplianceConstants.AC:
                      return new AC(countOfAppliance,perDayUsage);
  
                  case ApplianceConstants.FRIDGE:
                      return new Fridge(countOfAppliance,perDayUsage) ;
  
                  default :
                      return new IElectricComponent() {
  
                          @Override
                          public int claculateUnitForSingleDay() {
                              // TODO Auto-generated method stub
                              return countOfAppliance*perDayUsage;
                          }
                      };
              }
  
          }
      }
  

  Constants:

  public interface ApplianceConstants {
  
      public String FAN = "Fan";
      public String LIGHT = "Light";
      public String AC = "AC";
      public String FRIDGE = "Fridge";
  
      public int Slab1 = 20;
      public int Slab2 = 30;
      public int Slab3 = 40;
      public int Slab4 = 50;
  }
  

  PriceSlab:

  public class PriceSlab {
  
      HashMap<String,Integer> slabs = new HashMap<>();
  
      public int calculateBill(int units){
  
          slabs.put("A", ApplianceConstants.Slab1);
          slabs.put("B", ApplianceConstants.Slab2);
          slabs.put("C", ApplianceConstants.Slab3);
          slabs.put("D", ApplianceConstants.Slab4);
  
          return calculateBillTotal(units);
      }
  
      private int calculateBillTotal(int units) {
  
          int total = 0;
          if(units <= 1000){
              total = units*slabs.get("A") ;
          }
          else if (units <= 3000){
              total = 1000*slabs.get("A") + (units-1000)*slabs.get("B");
          }
          else if (units <= 6000){
              total = 1000*slabs.get("A") + 2000*slabs.get("B") +(units-3000)*slabs.get("C");
          }
          else{
              total = 1000*slabs.get("A") + 2000*slabs.get("B") + 3000*slabs.get("D")
                  +(units-6000)*slabs.get("C");
          }
          return total;
      }
  }
  

  Main class:

  public class BillGenerator {
  
      public static void main(String[] args) {
  
          Scanner scn = new Scanner(System.in);
          ApplianceFactory factory = new ApplianceFactory();
          int inputOfAppliance = scn.nextInt();
          String appliance="";
          int countOfAppliance;
          int perDayUsage;
          int unitsPerDay=0;
          for(int t=0 ; t<inputOfAppliance ;t ++){
              appliance = scn.next();
              countOfAppliance = scn.nextInt();
              perDayUsage = scn.nextInt();
              IElectricComponent electricComponent = factory.getInstance(appliance, countOfAppliance, perDayUsage);
              unitsPerDay += electricComponent.claculateUnitForSingleDay();
          }
          System.out.println("unitsPerDay = "+unitsPerDay);
          int unitsPerMonth = unitsPerDay * 30;
          System.out.println("unitsPerMonth = "+unitsPerMonth);
  
          PriceSlab slab= new PriceSlab();
          int totalBill = slab.calculateBill(unitsPerMonth);
          System.out.println("totalBill = "+totalBill);
      }
  
  }
  

  I thought a lot about how to remove hardcoding from price-slab function but couldn't think of anything better. Please let me know how it can be improved or if any other design pattern could be used for it.

  Thanks in advance.
• C++: How do I pass a derived object into a class that holds its abstract base?

  I have a class which I want to hold an abstract class object.

  class myClass
  {
  abstractClass abstractObject; //won't work since abstractClass is abstract
  // ....
  }
  

  where abstractClass is an abstract base class. Then I might have a non-abstract derivedClass1 and derivedClass2, both of which inherit from abstractClass. I want to pass these derived class into myClass. How do I do this using rvalues?

  I want to be able to e.g. say

  myClass someOBJ(derivedClass1(x, y, z));
  myClass someOtherOBJ(derivedClass2(x,y,z));
  

  and then these two objects now hold objects of type derivedClass1 and derivedClass2.
• What is the best way to provide access to a PHP class from another class?

  I need to scrape a webpage and check to see if it's displaying any errors. I then need to log those errors in a database.

  I've written a class, ErrorChecker, that handles the scraping. I have a second class, DB, that handles all database operations. The third class, Logger, looks at the errors and does some processing on them before sticking them in the database. (EG: Has this already been logged?)

  These three classes obviously interact. I'm looking for the best approach to handling this from a maintainability standpoint. Here are my thoughts.

  Option 1: Instantiate the DB and ErrorChecker objects in the "Parent" script (index.php) then pass them into Logger through its constructor.

  Option 2: Add a "require_once" statement for DB and ErrorChecker inside of Logger. Instantiate those objects from within Logger.

  Option 3: Instantiate all the objects in the "Parent" script (index.php) and don't pass anything anywhere. Handle any logic where they intersect in the top level script.

  Sorry if I messed up any terminology. I'm just legitimately not sure what best practice is here and would like to avoid having a mess or needing to do major refactoring later. Thanks in advance!
• C++ error: "expected constructor, destructor or type conversion before "(" token

  I've made this small c++ program and whatever I do, I can't get rid of the error in the title. I've tried everything and I have no idea what to do. Maybe the compiler for some reason doesn't recognize Cloth as the enter code hereconstructor, but I'm not sure about it. Including either "using namespace std" line or std:: suffix results only in getting 3 more errors, along with the previous one. Any halp would be very appreciated. Thank you in advance.

  Here's the code:

  main:

  #include <iostream>
  #include <string>
  #include <vector>
  #include "Cloth.h"
  
  using namespace std;
  
  int main()
  {
      vector <Cloth> clothRegistry;
      string entry1;
      int entry2;
      while (entry1 != "q" || entry2 != 101010)
      {
          cin >> entry1;
  
          // "q" quits the program in entry1;
  
          if (entry1 == "centry")
          {
              cin >> entry2;
          }
  
          else if (entry1 == "add")
          {
              add (string clothName, string clothType);\
              cin >> entry1;
          }
  
          else if (entry1 == "del")
          {
              del (string clothName);
              cin >> entry1;
          }
  
          else if (entry1 == "report")
          {
              report (string clothName);
              cin >> entry1;
          }
  
          else if (entry1 == "clean")
          {
              clean (string clothName);
              cin >> entry1;
          }
  
          else if (entry1 == "check")
          {
              check (string clothName);
              cin >> entry1;
          }
  
          else if (entry1 == "view all")
          {
              view_all ();
              cin >> entry1;
          }
  
          else if (entry1 == "view ::t_shirt")
          {
              view_t_shirt ();
              cin >> entry1;
          }
  
          else if (entry1 == "view ::short_shirt")
          {
              view_short_shirt ();
              cin >> entry1;
          }
  
          else if (entry1 == "view ::shirt_complex")
          {
              view_shirt_complex ();
              cin >> entry1;
          }
  
          else if (entry1 == "view ::shirt_pattern")
          {
              view_shirt_pattern ();
              cin >> entry1;
          }
  
          else if (entry1 == "view ::shirt_plain")
          {
              view_shirt_plain ();
              cin >> entry1;
          }
  
          else if (entry1 == "view ::trousers")
          {
              view_trousers ();
              cin >> entry1;
          }
  
          else if (entry1 == "view ::short_trousers")
          {
              view_short_trousers ();
              cin >> entry1;
          }
  
         else if (entry1 == "help")
          {
              help ();
              cin >> entry1;
          }
  
          else
          {
              cout << "ERROR: Bad command name." << endl;
              cin >> entry1;
          }
  
          // "101010" quits the program in entry2;
  
          if (entry2 == 1)
          {
              cin >> entry1;
          }
  
      }
      return 0;
  }
  

  Cloth.h:

  #ifndef CLOTH_H_INCLUDED
  #define CLOTH_H_INCLUDED
  #include <iostream>
  
  
  class Cloth
  {
     public:
  
     Cloth(std::string m_clothName = "unknownName", std::string  m_clothType = "unknownType", std::string m_laundryStatus = "OK", int m_wearingNumber = 0); // here's where the error occurs
     std::string getClothName() const;
     std::string getClothType() const;
     std::string getLaundryStatus() const;
     int getWearingNumber() const;
     void show (std::ostream &flux) const;
  
  
     private:
  
     std::string m_clothName;
     std::string m_clothType;
     std::string m_laundryStatus;
     int m_wearingNumber;
  };
  
  std::ostream& operator<< (Cloth const& a, std::ostream &flux);
  void add (std::string clothName, std::string clothType);
  void del (std::string clothName);
  void report (std::string clothName);
  void clean (std::string clothName);
  void check (std::string clothName);
  void view_all ();
  void view_t_shirt ();
  void view_short_shirt ();
  void view_shirt_complex ();
  void view_shirt_pattern ();
  void view_shirt_plain ();
  void view_trousers ();
  void view_short_trousers();
  void help();
  
  
  
  #endif // CLOTH_H_INCLUDED
  

  Cloth.cpp:

      #include "Cloth.h"
  
  Cloth::Cloth(string clothName, string clothType, string laundryStatus, int wearingNumber) : string m_clothName(clothName), string m_clothType(clothType), string m_laundryStatus(laundryStatus), int m_wearingNumber(wearingNumber)
  {
     if (m_clothType = "::t-shirt" || "::short_shirt" || "::shirt_complex" || "::shirt_pattern" || "::shirt_plain")
     {
         if (wearingNumber < 3)
         {
             m_laundryStatus == "OK";
         }
         else
         {
             m_laundryStatus == "WASH";
         }
     }
     else if (m_clothType = "::trousers" || "::short_trousers")
     {
         if (wearingNumber < 7)
         {
             m_laundryStatus == "OK";
         }
         else
         {
             m_laundryStatus == "WASH";
         }
     }
     else
     {
         cout << "BASE ERROR: no such cloth type to initialize m_laundryStatus check." << endl;
     }
  }
  
  string Cloth::getClothName() const
  {
       return m_clothName;
  }
  
  string Cloth::getClothType() const
  {
      return m_clothType;
  }
  
  string Cloth::getLaundryStatus() const
  {
      return m_laundryStatus;
  }
  
  int Cloth::getWearingNumber() const
  {
      return m_wearingNumber;
  }
  
  void Cloth::show(ostream& flux) const
  {
      flux << m_clothName << " " << m_clothType << " " << m_wearingNumber << " " << m_laundryStatus;
  }
  
  ostream& operator<< (Cloth const& a, ostream& flux)
  {
      a.show(flux);
      return flux;
  }
  
  void add (string clothName, string clothType)
  {
      int clothNamingNumber;
      cout << "New cloth name:" << endl;
      cin >> clothName;
      cout << "New cloth type:" << endl;
      cin >> clothType;
      while (cloth type != "::t_shirt" || "::short_shirt" || "::shirt_complex" || "::shirt_pattern" || "::shirt_plain" || "::trousers" || "::short_trousers")
      {
          cout << "INPUT ERROR: no such cloth type" << endl;
          cin >> clothType;
      }
      for (int i, i>0, i++)
      {
          clothNamingNumber == i;
      }
      Cloth clothNamingNumber(clothName, clothType, 0, "OK");
      clothRegistry.push_back(clothNamingNumber);
      cout << "Object" << clothName << "has been added to clothRegistry"  << endl;
  }
  
   void del (string clothName)
   {
      cout << "Cloth name:" << endl;
      cin >> clothName;
      for (int i = 0, i <= clothRegistry.size(), i++)
      {
          if (i.getClothName() = clothName);
          {
              clothRegistry.erase(i);
          }
      }
  }
  
  void report (string clothName)
  {
      for (int i = 0, i <= clothRegistry.size(), i++)
      {
          if (i.getClothName() == clothName)
          {
              i.getWearingNumber()++;
          }
      }
  }
  
  void clean (string clothName)
  {
      for (int i = 0, i <= clothRegistry.size(), i++)
      {
          if (i.getClothName() == clothName)
          {
              i.getWearingNumber() == 0;
          }
      }
  }
  
  void check (string clothName)
  {
      cout << "Enter cloth name:" << endl;
      cin >> clothName;
      for (int i = 0, i <= clothRegistry.size(), i++)
      {
          if (i.getClothName() == clothName)
          {
              cout << i << endl;
          }
      }
  }
  
  void view_all ()
  {
      for (int i, i <= clothRegistry.size(), i++)
      {
          cout << clothRegistry[i] << endl;
      }
  }
  
  void view_t_shirt ()
  {
      for (int i, i <= clothReistry.size(), i++)
      {
          if (i.getClothType == "::t_shirt")
          {
              cout << clothRegistry[i] << endl;
          }
     }
  }
  
    void view_short_shirt ()
    {
        for (int i, i <= clothRegistry.size(), i++)
        {
            if (i.getClothType == "::short_shirt")
            {
                cout << clothRegistry[i] << endl;
            }
        }
    }
  
    void view_shirt_complex ()
    {
        for (int i , i <= clothRegistry.size(), i++)
        {
            if (i.getClothType == "::shirt_complex")
            {
                cout << clothRegistry[i] << endl;
            }
        }
    }
  
    void view_shirt_pattern ()
    {
        for (int i , i <= clothRegistry.size(), i++)
        {
            if (i.getClothType == "::shirt_pattern")
            {
                {
                    cout << clothRegistry[i] << endl;
                }
            }
        }
    }
  
    void view_shirt_plain ()
    {
       for (int i, i <= clothRegistry.size(), i++)
       {
           if (i.getClothType == "::shirt_plain")
           {
               cout << clothRegistry[i] << endl;
           }
       }
    }
  
    void view_trousers ()
    {
        for (int i, i <= clothRegistry.size(), i++)
        {
            if (i.getClothType == "::trousers")
            {
                cout << clothRegistry[i] << endl;
            }
        }
    }
  
    void view_short_trousers ()
    {
        for (int i , i <= clothRegistry,size(), i++)
        {
            if (i.getClothType == "::short_trousers")
            {
                cout << clothRegistry[i] << endl;
            }
        }
    }
  
    void help ()
    {
        cout << "CLOTH MANAGER HELP PAGE" << endl;
        cout << "add - adds new cloth to the registry" << endl;
        cout << "del - deletes the cloth" << endl;
        cout << "report - reports a single use of a cloth" << endl;
        cout << "clean - clears the cloth's usage log" << endl;
        cout << "check - checks the status of a cloth" << endl;
        cout << "view - shows a list of all the cloths or cloths of a particular kind" << endl;
        cout << "help - shows the help page" << endl;
    }
  
• Calculate the volume of cylinder with JavaScript using prototype

  I'm a javascript noob and beginner so don't get too hard on me.

  I need to calculate the volume of a cylinder using a constructor function and prototype.

  I've got a form with two inputs wich i'll be getting the values from to do the calculation with. I have to create a new instance when the button is clicked and the calculation has to be outputted in the outcome input.

  I seem to be stuck at the part to get the values out of the inputs as my console always says that 'hoogte' and 'diameter' is undefined when I click the button.

  I've been looking at this for almost 24h now, but i'm not getting any progress..

  This is my code:

  <form action="">
      <label>
          Diameter: <input type="text" id="diameter"><br><br>
          Hoogte: <input type="text" id="hoogte"> <br><br>
          <input type="button" value="bereken" id="berekenBtn"><br><br>
          <input type="text" id="uitkomst">
      </label>
  </form>
  

  -

  <script>
      window.addEventListener("DOMContentLoaded", function () {
          document.getElementById("berekenBtn").addEventListener("click", bereken);
      });
  
      function Cylinder(hoogte, diameter) {
          this.hoogte = hoogte;
          this.diameter = diameter;
      }
  
      Cylinder.prototype.volume = function () {
          var radius = document.getElementById('diameter') = this.diameter / 2;
          var hoogte = document.getElementById('hoogte') = this.hoogte;
  
          var berekening = Math.PI * radius * radius * hoogte;
          //berekening.toFixed(4);
      }
  
  
      function bereken() {
          var myCylinder = new Cylinder(
              document.getElementById("uitkomst").value = Cylinder()
          )
          console.log(myCylinder);
      }
  </script>
  
• Sklearn supervised learning with 3d array

  NOTE: You can probably ignore the paragraph below if you have deep technical knowledge of sklearn and ML in general.

  I am working on indexing image objects based on their position in an image. Their index is relative to the other image objects in each image,which varies significantly, so simple math will not work in indexing them. Moreover, I have tried to index them via their middle x coordinate in the image, but that only yields an accuracy of ~75% with sklearn DecisionTreeRegressor. Now I want to try to train a model to index them from their detection box's (obtained from tensorflow object recognition + pretrained neural network) x1,y1 or x1,x2,y1,y2 coordinates.

  So here's my question:

  Is an array such as

  [
    [[x0_0_0, x0_0_1], # <- object 1 x,y coords for image 1
    [x0_1_0, x0_1_1]], # <- object 2 x,y coords for image 1
    [      ...      ],
    [[xn_0_0, xn_0_1], # <- object 1 x,y coords for image n
    [xn_1_0, xn_1_1]]  # <- object 1 x,y coords for image n
  ]
  

  with a target array of

  [[y0_0, y0_1], # <- indices of objects 1 and 2 in image 1
   [   ...    ],
   [yn_0, yn_1]] # <- indices of objects 1 and 2 in image n
  

  Viable for use in any supervised ML algorithms packaged in sklearn?
• Clear references to function

  I need to clear memory in js, I have classes like this:

  class A{
    constructor(socket){
      this.initSockets(socket);
    }
  
    classMethod(){
  
    }
  
    initSockets(socket){
      socket.on('name', () => this.classMethod())
    }
  }
  

  This class cannot be cleaned by the garbage collector, because as I understand socket saves the reference to a class method(memory snapshot point to socket.on), how properly I need "to null" this function, to delete the reference and let garbage collector delete this class? The project becomes a little big, so I can't change the way I use sockets.
• C++: References to pointers mixed with vectors. I'm having trouble with it

  I'm a newbie in programming, but have studied some C and Java.

  I'm now beginning to study C++. One of the first exercises I assigned for myself was to translate a small program written in Java to C++. Now, as I understand it, Java seems to use pointers to objects for everything behind the scenes (what is called in Java "reference variables") or addresses to objects (what is called in Java "reference"), hence why you can't directly manipulate objects like in C++, instead using the "reference" for it.

  Because of that, I wanted to write this program the closest as possible to this Java logic, using pointers for any object instead of using objects themselves. However I ran into a problem while trying using range-based loops (for-each) with vectors. The only workaround I found was to use a traditional loop (regular for) or to just ditch this Java logic and use objects directly. I want however to use pointers, not the objects themselves.

  Is it really impossible? If not, what do I have to change in my code?

  #include <iostream>
  #include <vector>
  
  using namespace std;
  
  class File;
  
  class FileGenerator {
      public:
          void generateFile(vector<File *> * &files);
  };
  class File {
      public:
          virtual void generate() = 0;
  };
  class FilePDF : public File{
      public:
          void generate();
  };
  class FileXML : public File {
      public:
          void generate();
  };
  
  void FileXML::generate(){
      cout << "Generating XML file... " << endl;
  }
  
  void FilePDF::generate(){
      cout << "Generating PDF file... " << endl;
  }
  void FileGenerator::generateFile(vector<File *> * &files){
      ///THIS WORKS FINE!
  //    for(int i = 0; i < files->size(); i++){
  //        files->at(i)->generate();
  //    }
      ///THIS DOES NOT WORK!
      for(File *file : *files){
          file->generate();
      }
  }
  
  int main(){
      vector<File *> *files = new vector<File *>;
      files->push_back(new FilePDF);
      files->push_back(new FileXML);
  
      FileGenerator *fileGenerator = new FileGenerator();
      fileGenerator->generateFile(files);
  
      return 0;
  }