this and super Keywords in Java: 17 MCQs with answers

C · The current object

`this` is a hidden reference to the object on which the method was invoked.

A · It refers to the parent part of the current object

`super` is a reference to the superclass slice within the current object, not a distinct object.

B · To assign the parameter to the instance field

`this.field` refers to the instance field, while `field` on the right is the parameter, resolving the name clash.

B · `this(...)`

`this(...)` invokes another constructor of the same class and must be the first statement.

B · Calls the parent's version of the method

`super.method()` explicitly invokes the superclass's implementation of the method.

A · True

`this(...)` and `super(...)` must be the first statement in a constructor, and a constructor cannot contain both.

A · Static methods have no current object

`this` requires an object instance; static methods belong to the class and have no instance.

A · A then B

`super.show()` calls the parent's `show()` first, printing "A", then the subclass prints "B".

D · Java inserts a hidden `super()` call

Java automatically inserts `super()` if no explicit constructor call is present, requiring the parent to have a no-argument constructor.

B · Returning `this` from a method for chaining

Returning `this` is a common pattern for method chaining; the other options are illegal.

D · The subclass field shadows the parent field

Field shadowing creates two separate fields; `this.field` accesses the subclass field, `super.field` accesses the parent field.

B · A constructor can contain at most one of them, as the first statement

Only one constructor call is allowed, and it must be the first statement.

D · To ensure the object is initialised before other code runs

The first-statement rule guarantees that the object is fully constructed before any other statements execute.

C · Explicitly call `super(x)` as its first statement

Since `Parent` lacks a no-argument constructor, the hidden `super()` would fail; `Child` must explicitly call `super(x)`.

C · Compilation error

`super.super` is illegal; you can only access one level up the inheritance hierarchy.

A · `super` is a keyword, not an object reference

`super` is a special keyword that refers to the parent slice; it is not a standalone object and cannot be stored or passed.

C · Some sound Bark

The correct output is 'Some sound Bark' because `super.sound()` calls the parent method from `Animal`, which prints 'Some sound', followed by the subclass `Dog` printing 'Bark'.