Conceptual Understanding

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來自 Duke University 的課程

Java 程序设计：使用软件解题

2353 個評分

Duke University

Java 程序设计：使用软件解题

2353 個評分

課程 1（共 4 門，Specialization Object Oriented Programming in Java）

Building upon Duke’s “Programming and the Web for Beginners” course, you will grow in your ability to be a problem-solver and programmer by writing Java programs. We are excited that you've chosen to learn Java with us! You will soon be able to solve problems that you find interesting and useful by practicing a design process you will learn in this course. Java concepts presented in this course include basic control flow; object-oriented concepts including classes and methods; custom, open-source classes; and a design-implement-debug process that you can continue to leverage as you build your experience and knowledge of programming principles. The custom, open-source classes will provide a consistent application programming interface (API) so that you can write programs that access and transform images, websites, comma separated value (CSV) files and other data files using simple and accessible coding idioms built on the Java Iterable interface. You will learn to design, test, and debug programs and to find and read Java documentation that can serve as the basis for continued study of Java and programming. After completing this course you will be able to: 1. Edit, compile, and run a Java program; 2. Use conditionals and for loops appropriately in a Java program; 3. Use Java API documentation in writing programs. 4. Debug a Java program using the scientific method; 5. Develop a Java method to solve a specific problem; 6. Develop a set of test cases as part of developing a program; 7. Create a class with multiple methods that work together to solve a problem; and 8. Use divide-and-conquer design techniques for a program that uses more than one method.

從本節課中

Strings in Java

This module begins with a short presentation from Raluca Gordân, an assistant professor in Duke University’s Center for Genomic and Computational Biology, about an important problem genomics scientists encounter regularly: how to identify genes in a strand of DNA. To tackle this problem, you will need to understand strings: series of characters such as letters, digits, punctuation, etc. After learning about Java methods that work with strings, you will be able to find genes within a DNA string as well as tackle other string related problems, such as finding all of the links in a web page. By the end of this module, you will be able to: (1) Use important methods for the Java String class; (2) Use conditionals, for loops, and while loops appropriately in a Java program; (3) Find patterns in the data represented by strings to help develop the algorithm for your program; (4) Understand the importance of designing programs that keep different data processing steps separate; (5) Use the StorageResource iterable for this course to store some data for further processing; and (6) Rely on Java documentation to better understand how to use different Java packages and classes.

Introduction0:48

Conceptual Understanding4:01

While Loops9:30

While Loop Syntax and Semantics3:06

Coding While Loops6:45

Three Stop Codons5:03

Coding Three Stop Codons - Part I7:45

Coding Three Stop Codons - Part II4:35

Logical And / Or8:01

Coding And / Or6:52

Finding Multiple Genes5:16

Translating to Code8:00

與講師見面

Owen Astrachan
Professor of the Practice
Computer Science
Robert Duvall
Lecturer
Computer Science
Andrew D. Hilton
Associate Professor of the Practice
Electrical and Computer Engineering
Susan H. Rodger
Professor of the Practice
Computer Science

Welcome back. In this lesson,

you're going to learn a powerful new programming construct, an indefinite loop.

You'll also learn about another Iterable from the edu.duke library.

You've already solved problems using the FileResource

and URLResource classes from the edu.duke library.

Using Iterables made it possible to repeatedly access data stored

in a file on your computer or via a URL from the World Wide Web.

You will use this concept of repetition to find all the genes in a strand of DNA,

a problem that genome scientists do as part of their work,

and a problem that models finding all links in a webpage,

or all the YouTube videos you might want to watch about cats or dragons or anything else.

The key idea here is that you'll use the algorithm from

a previous lesson that found one gene in a strand of DNA,

an algorithm you've tested and have confidence in.

You'll repeatedly apply this algorithm over

the entire strand of DNA to find all genes, not just one.

You'll also learn about a new Iterable that lets you store intermediate results.

Instead of printing all the genes you find,

you'll be able to store them so that you can look for

particular genes after you found strings that could be genes, for example.

By storing the results of a gene search or other kinds of search,

you can write separate methods to process

the genes rather than including the processing with the finding.

This separation of concerns find genes, process genes.

Filter any of those genes that have specific characteristics,

is a hallmark of good software engineering.

Writing a method to do one thing rather than doing several things.

This separation allows you to reuse code more easily and to develop a code more easily.

The storage you use will be an Iterable you can add to,

while the program you write is running.

To be more concrete,

you're going to solve a variation of a problem you solved once before.

The problem of finding a gene in a strand of DNA.

Genes are found in a strand of DNA at different sites within the DNA.

In a previous lesson, you developed code for finding

one gene like the region shown in red here.

You found this gene by looking for particular markers

called start codons and stop codons.

These markers were used to identify the part of a string that could be a gene.

You could have used a similar algorithm to find

where a link occurs in the html text of a webpage.

Looking for a href rather than ATG for example.

DNA typically carries more than one gene, however.

So, rather than finding this one gene that's marked in red,

you'll use programming techniques to find

all the regions in a strand of DNA that could code for a gene.

Regions that begin with a start codon as shown here,

but that also are indicated by one of three stop codons.

In the next group of lessons,

you'll learn many things about Java and

programming as you practice solving this gene finding problem.

You'll learn how to repeat a process many

times even when you don't know how many times this is.

You'll do this by using a while loop;

a new kind of loop, that complements the for loop you've used with Iterables.

You'll learn about the storage resource class,

from the edu.duke library.

Using a storage resource object will allow you to add selected values to the storage,

and then access them in your code using

the standard for loop with Iterables you've used before.

This storage will also be a preview of

future programming technique you'll learn about using arrays to store values.

You will also practice with developing if statements,

and Boolean expressions that use what's called short-circuit evaluation.

This will be an important part of the practice and knowledge you'll gain as you

move toward becoming a better programmer and problem solver. Thank you.

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