Coding StorageResource Class

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Java 程序设计：使用软件解题

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Duke University

Java 程序设计：使用软件解题

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课程 1（共 4 门，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.

从本节课中

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.

Separation of Concerns5:07

StorageResource Class3:54

Coding StorageResource Class4:27

与讲师见面

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

All right, so you've learned that what you would like to do now is

separate finding the genes from printing the genes.

And the way we are going to do this is we're going to take all the genes you find

and put them in a storage resource.

Then you can iterate over that storage resource and print them out.

Or if you wanted to do other things with the genes once you've found them,

filter them, calculate properties about them, whatever.

You could iterate over the storage resource and do those without

reduplicating all of your code to have another thing that finds them all.

So I've taken our code that prints all the genes which we developed in a previous

video and I've made a couple small changes to it.

So I changed it from being called printAllGenes to getAllGenes since we're

going to get them instead of print them.

It returns a StorageResource now because that's what it's going to give back as its

answer, one of these things that holds all of these strings.

I've altered the comments here with the steps to the ones that we developed in

the previous video where we came up with the algorithm.

And where these have been the same as before, which is most of the steps,

I've left that code.

For one of these,

where we were previously printing it and are now adding it to a list.

I deleted the old code, the System.out.println, which we don't want.

But otherwise this is pretty much the same.

And then, in our test methods, I've removed that code,

because we're going to have to do something a little bit different.

So let's start by turning these steps into code.

Now the first thing we want to to is create an empty storage resource and

call it geneList.

So geneList is going to be a new variable.

We need to declare that its type is StorageResource.

geneList is its name.

And it's going to be an empty StorageResource,

a new one with nothing in it.

It's going to be a new StorageResource.

And then these steps are already translated to code until we get down here

to where we want to take that gene and add it to our gene list.

So that's just going to be geneList.add(gene);.

And then at the end here, our answer is geneList.

As you've seen many times by now, when your method or function knows its answer,

it returns that answer to whoever called it.

Okay?

So now I want to write my method that's going to test this.

And we're going to test it by printing things out.

So the behavior of our code is going to be just what we did before but

it's going to be more useful.

More reusable,

we can put it to other purposes than just printing out these genes.

So the first thing I want to do is call this method,

getAllGenes, that we just finished writing.

And store its result in a StorageResource variable.

Store, which I'm not sure I can spell.

We'll just call this genes = getAllGenes on that DNA.

Now we want to iterate over the things in it.

So I have here the Duke Learn to Program documentation

because I'm not very familiar with StorageResource.

It's not one of the standard Java classes.

It's kind of a nice simplification for you.

If I didn't remember how to iterate over all of these things

I could look at this and say okay, add, we just used that.

Size.

.data returns an iterable.

Those are the things that we can write for each loops.

It even gives us this little example here.

So what we're going to do is for All of the strings,

all of the genes which are strings in these genes we just got back,

we want to print that particular gene out.

I'm going to hit Compile.

Whoops.

Up here this was called currentGene.

Java is fussing at me because it has no variable there called just gene.

Fix that.

And here, [SOUND], whoops, I looked up the method and then I forgot to call it.

That was good, easy to fix.

I'm going to get rid of this documentation.

I'm going to come over here, and I'm going to make a new one of these.

And then I'm going to run it.

And it ran just fine and gave me the same results as before.

But our code is now more reusable.

We could put it to other purposes more easily.

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