Instantiating object in a constructor

Question

It seems that the result of the following code is the same, so when should I use each?

public class Person {
   public Person() {
       this.family = new Family();
   }
   Family family;
}

to

public class Person {
   Family family = new Family();
}

(one scenario I can think of, is when having multiple constructors and we want to create an instance of family only inside one of them... is that the only case?)

Answer 1

For class variables [static variable] you cannot use the first, since you want the initializtion to happen only once, and not with every time you invoke your constructor.

For instance variables, the second is just a syntatic sugar of the first.
Sometimes you might have to use the second - for argument constructor, which are themselves - passed to your constructor.