0 Java knows that a method is a constructor because it has the same name as the class itself and no return value.

1 Constructors can not be inherited

2 When declaring constructors for your class, you can use the normal access specifiers to specify what other objects can create
instances of your class.

3 Either this or super can be called as the first line from within a constructor, but not both (or compiling error). Note that This is true if this or super is used to invoke a constructor; if you use this or super to invoke a method, you can place them anywhere
anytimes.

class Base{
  public Base(){}
  public Base(int i){}
}

public class MyOver extends Base{
  public static void main(String arg[]){
    MyOver m = new MyOver(10);
  }
  MyOver(int i){
    super(i);
  }
  MyOver(String s, int i){
    this(i);
  }
}

4 Constructors are called from the base (ancestor) of the hierarchy downwards.

class Mammal{
  Mammal(){
    System.out.println("Creating Mammal");
  }
}

  public class Human extends Mammal{
  public static void main(String argv[]){
    Human h = new Human();
  }
  Human(){
    System.out.println("Creating Human");
  }
}

The output of above is:
"Creating Mammal"
"Creating Human"