Where must super() be placed in a subclass constructor?

Where must super() be placed in a subclass constructor?

• A. As the very first statement
• B. Anywhere in the constructor
• C. At the end of the constructor
• D. In a static block

Answer: (A)

The important idea is that the superclass part of an object must be set up before the subclass adds its own initialization. In languages like Java, if you want to call a specific superclass constructor, that call must be the very first statement in the subclass constructor. This guarantees the parent’s fields and invariants are initialized before the subclass proceeds with its own initialization. If you put other code before the superclass call, you would be trying to operate on an incompletely initialized object, which is not allowed and leads to errors. If you don’t specify a superclass call, the language automatically inserts a default no-argument super() call as the first line, still ensuring the parent is initialized first. Static blocks don’t belong in a constructor at all, since they run when the class is loaded, not when an instance is created.

The important idea is that the superclass part of an object must be set up before the subclass adds its own initialization. In languages like Java, if you want to call a specific superclass constructor, that call must be the very first statement in the subclass constructor. This guarantees the parent’s fields and invariants are initialized before the subclass proceeds with its own initialization. If you put other code before the superclass call, you would be trying to operate on an incompletely initialized object, which is not allowed and leads to errors. If you don’t specify a superclass call, the language automatically inserts a default no-argument super() call as the first line, still ensuring the parent is initialized first. Static blocks don’t belong in a constructor at all, since they run when the class is loaded, not when an instance is created.