Why call to this () must be the first statement in constructor?

this or super needs to be first statement in constructor so that child class constructor invokes parent class constructor first . This is required to initialize any variable in parent class before doing any thing in child constructor.

The reason is that “Constructor call must be the first statement in a constructor”.

The Eclipse compiler says “Constructor call must be the first statement in a constructor”. So, it is not stopping you from executing logic before the call to super . It is just stopping you from executing logic that you can’t fit into a single expression. There are similar rules for calling this().11 Tem 2019

Historically, this() or super() must be first in a constructor . This restriction was never popular, and perceived as arbitrary. There were a number of subtle reasons, including the verification of invokespecial, that contributed to this restriction.12 Mar 2017