Chapter 10 - Arrayslist/Java Collections

Question 1

What does the ArrayList class provide?

Answer 1

The basic functionality that comes with a standard array, plut it provides additional functionality

Question 2

What is the basic functionality of an ArrayList?

Answer 2

Stores an ordered collection of values and allows access to the value via an index.

Question 3

What is the added functionality of an ArrayList?

Answer 3

Grows and shrinks dynamically by inserting and deleting elements at any specified location.

Question 4

What do you type to import the ArrayList class?

Answer 4

import java.util.ArrayList;

Question 5

How do you initialize an ArrayList reference variable?

Answer 5

Use this syntax in a declaration:

ArrayList(Student) variablename = new ArrayList<>();

It should be angled brackets around Student instead of parathesis <>

Question 6

Comparative Syntax for creating ArrayList objects, regular objects and standard Arrays

Answer 6

Question 7

What syntax adds and element to the end of an ArrayList?

Answer 7

ArrayList-reference-variable.add(item);

The “item” that’s being added must be the same type as the type specificied in the ArrayList’s declaration.

Question 8

What does API stand for?

Answer 8

Application Programming Interface

Question 9

What is the Java API?

Answer 9

The interface to the huge libaray of pre-built Java classes.

Question 10

What do you have to use to interface with with Java API classes?

Answer 10

Their public methods

Question 11

What information do you have to know to use a public method?

Answer 11

The type of argument to pass to it, and what type of value it returns.

Question 12

What does a method’s API show?

Answer 12

The method’s parameters and its return type.

Question 13

ArrayList objects don’t use square brackets like standard arrays when accessing and updating an element, what do they use instead?

Answer 13

A get method to access the element

A set method to update and element

Question 14

What does the E return type in the ArrayList’s get method mean?

Answer 14

It stands for element. Represents the data types of the ArrayList’s elements.

It should be the same as the element-type specified in the ArrayList’s initialization:

ArrayList(element-type) reference-variable = new ArrayList<>();

It should be angled brackets around element-type <>

Question 15

What does the set method allow you to do?

Answer 15

Assign a value to an existing ArrayList.

API heading example:

public E set(int index, E elem)

Question 16

What does the following Syntax do?

public void add(int index, E elem)

Answer 16

Starting with the specified index position, shift the original elements to higher-indexed positions. Then insert the elem parameter at the specified index position.

Question 17

What does the following Syntax do?

public void clear()

Answer 17

Removes all elements from the list.

Question 18

What does the following Syntax do?

public int indexOf(Object elem)

(Object is a generic class that can be used as a class type for any object)

Answer 18

Search for the first occurrence of the elem parameter within the list. If it’s found, return its index position. If it’s not found, return -1.

Question 19

What does the following syntax do?

public boolean isEmpty()

Answer 19

Return true is the list contains no elements.

Question 20

What does the following syntax do?

public E remove(int index)

Answer 20

Remove the element at the specified index position, shift all higher-indexed element to lower-indexed positions, and return the removed element.

Question 21

What does the following syntax do?

public int size()

Answer 21

Return the number of elements in the list.

Question 22

What is the output if you print of concatenate an ArrayList?

Answer 22

A comma-seperated list of ArrayList elements surrounded by square brackets.

Question 23

How do you store primitives in an ArrayList?

Answer 23

You have to wrap the primitives in wrapper classes.

In Java 5.0 and higher it’s done automatically if a wrapper class is used in an ArrayList declaration.

Question 24

When storing objects in an ArrayList can you create and object and add it to the ArrayList in the same statement?

Answer 24

Yes

Question 25

What is an anonymous object?

Answer 25

An object that's instantiated, but it's not stored in a variable

Question 26

What two situations are anonymous objects typically used in?

Answer 26

- Passing a new created object into a method or constructor. bears. add(new Bear("Acme", "brown teddy")); - Returning a newly created object from a method. return new Bear(maker, type);

Question 27

What does "for-each loop" syntax look like in an *ArrayList?*

Answer 27

for ("element-type" "element-name" : "ArrayList-reference-variable") example: for (Bear bear : bears)

Question 28

What are the benefits of an *ArrayList* over a standard Array?

Answer 28

- It's easy to increase the size of an ArrayList - just call *add* - It's easy for a programmer to insert or remove an element to or from the interior of an ArrayList - just call add or remove and specify the element's index position

Question 29

What are the benefits of a standard array over an *ArrayList?*

Answer 29

- A standard array uses []'s to access array elements (which is easier than using get and set methods) - A standard array is more efficient with storing primitive values

Question 30

What is a *LinkedList* Class?

Answer 30

Similar to an ArrayList in that is hold a collection of related data, but instead of using an underlying array to store the data, it uses a chain of references.

Question 31

What methods do *ArrayList* and *LinkedList* implement the same?

Answer 31

get, set, add, remove, clear, and size

Question 32

Why do *ArrayList* and *LinkedList* implement many of the same methods?

Answer 32

Because they both implement the same List interface

Question 33

What are *implements?*

Answer 33

They mean the class promises to implement all methods specified by the interface.

Question 34

What does the syntax look like for declaring a variable with an interface at the left?

Question 35

What are the beneifts of a *LinkedList* over and *ArrayList?*

Answer 35

- It's easier to find, add, or remove element that are near one of the two ends. - Once an element has been found, it's easier to remove it from a *LinkedList* (you just change a pair of references) rather than an *ArrayList* (shift all higher elements to lower array indices)

Question 36

What are the benefits of an *ArrayList* over a *LinkedList*?

Answer 36

Finding an indexed element is much faster than a *LinkedList.*

Question 37

What is a *queue*?

Answer 37

A first-in first-out (FIFO) waiting line.

Question 38

In a queue what order do you add and remove elements?

Answer 38

Add elements to the back (tail) and remove elements from the front(head).

Question 39

What class is the most efficient for implementing queues?

Answer 39

*ArrayDeque*

Question 40

What is *ArrayDeque* backed by?

Answer 40

An Array

Question 41

What is the length of the Array that *ArrayDeque* is backed by?

Answer 41

Initially 16, but its length doubles each time the current length is inadequate.

Question 42

What are the other traits of the backing array for *ArrayDeque?*

Answer 42

- It is circular, meaning links connect opposite ends - Pointers identify current head and tail elements - Adding increments tail point, deleting increments head point.

Question 43

What is the syntax to access *ArrayDeque*?

Answer 43

import java.util.\*;

Question 44

What is a stack?

Answer 44

A last-in first-out(LIFO) storage container.

Question 45

How does a stack add or remove elements?

Answer 45

It adds (push) and removes (pop) elements at the top.

Question 46

What are the two Java collections framework interface hierarchies?

Answer 46

- Collection hierarchy - Map hierarchy

Question 47

What methods does the *Collection* interface specify?

Answer 47

One that are common to the List, Queue, and Set interfaces. Such as, add, contains, isEmpty, set, size, and remove.

Question 48

What do classes that implement the *Collection* interface provide?

Answer 48

A one-parameter constructor that converts any type of collection to any other type of collection.

Question 49

What is the special queue included in the collection hierarchy?

Answer 49

A priority queue, which inserts higher priority elements closer to the head of the queue.

Question 50

What are the properties of a map?

Answer 50

Has a unique key, like an id number. This provides rapid access to other (more complex) objects.

Question 51

Java Collections Framework example

Answer 51

Question 52

Java Collections Framework - Maps example

Answer 52

Question 53

How does a map work?

Answer 53

It relates an object in a key set to another object that could be in another set, a list, or a queue.

Question 54

What is the input/output for a map?

Answer 54

The user provides an independent *key* and it returns a dependent *value.*

Question 55

How do you add, retrieve, and remove values in a map?

Answer 55