Structured Data

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Del curso dictado por Vanderbilt University

Java for Android

978 calificaciones

Vanderbilt University

Java for Android

978 calificaciones

Curso 1 de 5 en SpecializationAndroid App Development

This MOOC teaches you how to program core features and classes from the Java programming language that are used in Android, which is the dominant platform for developing and deploying mobile device apps. In particular, this MOOC covers key Java programming language features that control the flow of execution through an app (such as Java’s various looping constructs and conditional statements), enable access to structured data (such as Java's built-in arrays and common classes in the Java Collections Framework, such as ArrayList and HashMap), group related operations and data into classes and interfaces (such as Java's primitive and user-defined types, fields, methods, generic parameters, and exceptions), customize the behavior of existing classes via inheritance and polymorphism (such as subclassing and overriding virtual methods). Learners will apply these Java features in the context of core Android components (such as Activities and basic UI elements) by applying common tools (such as Android Studio) needed to develop Java programs and useful Android apps. Learners will work on several hands-on projects throughout the MOOC, i.e., each week will require learners to write solutions to programming assignments that reinforce the material covered in the lecture videos. There will be roughly 4-6 hours of student engagement time per week, including video lectures, quizzes, and programming assignments.

De la lección

Module 5: Structured Data

Module 5 provides more detail on common data structures supported by Java, including built-in arrays, as well as core classes in the Java Collections Framework, such as ArrayList and HashMap.

Structured Data3:26

Conoce a los instructores

Dr. Jerry Roth
Professor of the Practice
Electrical Engineering and Computer Science
Dr. Julie L. Johnson
Instructor
EECS
Michael Walker
Instructor - Graduate Student pursuing PhD in Computer Science
EECS
Dr. Douglas C. Schmidt
Professor of Computer Science and Associate Chair of the Computer Science and Engineering Program
Electrical Engineering and Computer Science

[MUSIC]

Welcome to the next module in our MOOC on Java for Android programming,

which focuses on constructs for storing and

processing collections of structured data within a single object.

After completing the lessons in this module, you will understand how Java

arrays work and how to access and process arrays efficiently.

You will also recognize the key classes and

interfaces in the Java collections framework.

Finally, we will explore several classes from this framework in detail,

including ArrayLists and HashMaps.

So you will learn how they work, what their pros and cons are, and

how to use them effectively to create android apps.

[MUSIC]

In this module, we are going to explore Java's capabilities for

storing structured data.

To help motivate the need for the subject, let's consider this sample problem.

Say we want to compute the average test score for

a classroom of students where the number of students may vary from class to class.

Giving this problem a little thought, we determine that we can

easily write a solution for this with the knowledge we have so far.

We can simply read in the number of students and

then create a cumulative sum loop that will read the specified number of times

and read in each student's score and add it to the total.

After reading all scores and exiting the loop, we can divide the total

by the number of students to compute and report the average.

It is a simple, straightforward solution.

Now, consider this slight twist to the problem.

Besides computing the average, we also want to report which

scores were below the average so that we can give extra help to those students.

To solve this new problem, we need each test score twice.

Once so we that can compute the average and then again to compare

against the average, we might be tempted to create a variable for each test score.

But since the number of students can vary,

we don't know how many variables to create.

And such code would become unruly if there were more than just a few students.

So with our current knowledge of Java,

we cannot come up with a good solution to this problem.

To solve this problem, we need a way to store a whole bunch of data together.

And we need to be able to treat the collection as a single entity but

still have access to any individual piece of data in the collection.

We need to be able to process all the data elements

in the collection in an easy manner.

And we need to access the elements as many times as needed and

in whatever order needed.

All of these are very important capabilities that we have carefully

avoided up to this point.

Java has several different solutions that we could apply to this problem and

to similar problems.

We will consider arrays first.

Since they are the oldest and

most standard structure found in programming languages.

In addition to arrays, Java also has a collections framework

which contains several structures that we can use.

The collections framework contains many structures, including lists, maps,

sets, cue's, et cetera.

The structures have different properties so that a program

can choose the most appropriate structure for any given problem.

For this class we only have time to look at ArrayList and HashMaps.

[MUSIC].

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