Compsci Quiz

What are wrapper classes

They provide a way to use primitive data types as objects.

Arraylist <int> → Why is this invalid

Collection classes only store objects. Primitive data types no work.

Collection

Container to hold multiple objects

Framework

Basic structure/toolkit to use something more efficiently.

Java framework

Ready made set of classes and interfaces with built in method you can use.

Collections framework

A set of classes and interfaces
Sorting, Searching, Inserting/Deleting, Data manipulation

Interface

Like a class but cannot be used to create an object.
Method signatures but no body.
Class can implement an interface

What can a class do with an interface that it cannot do with other classes

A class can implement multiple interfaces (like a contract), but cannot extend multiple classes.
It is REQUIRED to override every method in the interface.  

List vs Set collections

List allows duplicates, set does not.

Use ArrayList when

Fast access to elements via index
You don’t need to frequently add/remove elements in the middle

Use LinkedList when

Efficient insertion/deletion in the middle
Random access is not a priority

What is abstraction

Hiding complex details and only showing what is necessary.
Abstract classes cannot be instantiated
Abstract methods must be implemented
Enforces and organizes

Interface vs abstract

Everything in interface is assumed to be abstract.
You can only extend one class, implement as many as you want. Every field in interface is static and final.