Interface, Types, and Typecasting + Polymorphism

Question 1

When a class implements an interface, it promises to provide _______ the behavior published by that interface.

Answer 1

ALL

Question 2

TRUE OR FALSE:

Interfaces cannot be instantiated

Answer 2

TRUE

Question 3

Every field declaration in the body of an interface is implicitly ___________________________.

Answer 3

public static final

Question 4

Methods in an interface are ____________

Answer 4

Abstract methods

Question 5

multiple interfaces gives the illusion of _____________

Answer 5

multiple inheritance

Question 6

The type of one object is converted to match the type of another object
reference

Answer 6

Type Casting

Question 7

T or F

Casts can be applied to both primitive data types and object references

Answer 7

T

Question 8

Types of Casting

Answer 8

Explicit Casting
char c = (char) i

Implicit Casting
float num = i

Question 9

Widening vs Narrowing Conversion

Answer 9

Narrowing conversion may cause less of precision and range (float to int / superclass to subclass)

Widening conversion may cause increase in precision and range
(int to float / subclass to superclass)

Question 10

In type casting objects, the cast must be to ________________________

Answer 10

subclass types, superclass types, or interfaces

Question 11

determines the operations an object can perform.

Answer 11

Type

Question 12

determines the implementation of its methods

Answer 12

Class

Question 13

is a side effect of Inheritance
and Typing

Answer 13

Polymorphism

Question 14

___________________ for Flexibility: helps us write code
that is easy to modify and extend.

Answer 14

Polymorphism

Question 15

it is the ability of the programming language to handle objects differently depending on their data type or class.

Answer 15

Polymorphism

Question 16

Parametric Polymorphism

Answer 16

Java Generics

Question 17

Java ArrayList Methods

Answer 17

ArrayList <Integer> integers = new ArrayList<Integer>();</Integer></Integer>

integers.add();
integers.remove;
integers.get(index);
ingeters.size();
integers.isEmpty()
integers.addAll(Arrays.asList(1,2));

for (String s : stringList) //Iterate thru the elements

Question 18

Keyword for using an interface

Answer 18

implements

Question 19

Types of Polymorphism

Answer 19

True Polymorphism
- Subtype/Inclusion Polymorphism - A subclass of a superclass can be used as a substitute for its superclass.

• Parametric Polymorphism - classes are written so generically that their methods can handle values identically without depending on their types.

Pseudo/Ad hoc Polymorphism
- Method overloading gives the illusion of parametric polymorphism.

Question 20

Example usage of Iterator Generic

Answer 20

Iterator <String> iter = stringList.iterator();</String>

while(iter.hasNext()){
Sysout(iter.next());
}

Question 21

Java HashMap
Methods

Answer 21

HashMap <Integer, String> studRec = new HashMap <Integer, String>();

studRec.put(202365908, “Myko”);

studRec.get(202365908)

//Check if key exists
studRec.containsKey(202365908)

//Returns all the keys
studRec.keySet();

Question 22

Narrowing conversions are possible if and only if the object came from a preceding widening
conversion.

Answer 22

TRUE