How can I Call to another constructor that must be the first statement in the constructor block?

 I think this speaks somewhat to Apex assuming so much from Java. Try the same thing with a Java compile if you want to solve constructor call must be the first statement in a constructor:

      public class HelloDog { public static void main(String[] args) { Dog myDog = new Dog(); System.out.print(myDog); } } class Dog{ protected String name; public Dog(){ this("Fido").name="Arf"; //this.name="Arf"; System.out.println("Inside no argument constructor of Dog class"); } public Dog(String name){ this.name = name; System.out.println("One arg constructor of Dog class"); } }

Gives the following compiler errors:

/HelloDog.java:15: error: call to this must be first statement in constructor
this("Fido").name="Arf";
.   ^
/HelloDog.java:15: error: void cannot be dereferenced
this("Fido").name="Arf";
.           ^

As Martin answered, the chained constructor returns void rather than the instance, so you can't chain anything to it. Calling the constructor and constructor chaining are two different things with very similar syntax. Personally I think the C# syntax makes constructor chaining clearer. Rather than being a special case of this that appears at the start of the constructor it has its own explicit syntax:

class Dog { protected String name; public Dog() : this("Fido") { } public Dog(String name){ this.name = name; } }
If you tried to do a public Dog() : this("Fido").name="arf" { in C# the compiler will look at you funny and ask where the missing { is. The constructor chaining here isn't a statement that can end in a semicolon. It's telling the compiler to chain the constructors together.

Hope the answer helped you!