What is the role of the newInstance method in Java?

Question

Java

According to the book Thinking Java, requires you to complete the exercise. So, first of all, I create a top class: Next, I create several interfaces.
public class TOP implements itf2, itf1{}

public interface itf1 {}
public interface itf2 {}
public interface itf3 {}

Next, I create several classes that are extensible in the hierarchy

public class DownA extends TOP implements itf1, itf2 {}
public class DownB extends DownA implements itf1, itf2, itf3{}
public class DownC extends DownB{}

And accordingly I create the main class with methods.

public class MainClass {
  private static Formatter f = new Formatter (System.out);
  
  private static void Title (){
    f.format("%-15s %10s %10s\n", "Class", "Interface", "Status");
    f.format("%-15s %10s %10s\n", "-----", "---------", "------");
  }
  
  private static void DataName (Class cc){
    f.format("%-15s %10s %10s\n", cc.getName(), " ", " ");
  }
  
  private static void DataInterface (Class cc){
    f.format("%-15s %10s %10s\n", " ", cc.getName(), cc.isInterface());
  }
  
  public static Class ShowDatas (Class cc){
    if (cc == null)
      System.exit(1);
    
    DataName (cc);
    
    for (Class face : cc.getInterfaces())
      DataInterface (face);
    f.format("%-15s %10s %10s\n", "-----", "---------", "------");
    
    Class up = cc.getSuperclass();
    return ShowDatas (up);
  }
  
  public static void main(String[] args) {
    Class c = null;
    Title ();
    
    try{
      c = Class.forName("Demo.DownC");
    } catch (ClassNotFoundException e){
      e.printStackTrace();
    }
    ShowDatas (c);
  }
}

Now, I need to do it as an array, for this I need to use newInstance. But the thing is, I don't understand what exactly it is for. Code example:
Top class:

public class TOP {
  private static int counter = 0;
  private long id = counter ++;
  
  public String toString (){
    return Long.toString(id);
  }
}

Next, I create an additional class and create an array of type List

public class DownClass <T> {
  private Class <T> type;
  private List <T> mylist;
  
  public DownClass (Class <T> type){
    this.type = type;
    mylist = Arrays.asList();
  }
  
  public List <T> arr (int size){
    
      try {
        for (int i=0; i!=size; i++)
        mylist.add(type.newInstance());// Добавляем экземпляр класса в массив.
      } catch (InstantiationException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
      } catch (IllegalAccessException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
      } 
      
      return mylist;
  }
  }

And accordingly I create the main class

public class MainClass {

  public static void main(String[] args) {
    DownClass DC = new DownClass (TOP.class); // Передаем экзепляр класса.
    System.out.println(DC.arr(10));

  }
 }

Why and for what purposes is the newInstance method used, how to use it correctly?

Answer 1

This is reflection. You have an unknown class type Class type. Next, you need to create a new instance of it for this, and dynamic class creation type.newInstance() is used.
Normally, this would be MyDataClass type. and accordingly type = new MyDataClass();