Maximum Temperature Refactored

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From the course by Duke University

Java Programming: Solving Problems with Software

1913 оценки

Duke University

Java Programming: Solving Problems with Software

1913 оценки

Course 1 of 4 in the Specialization Object Oriented Programming in Java

Learn to code in Java and improve your programming and problem-solving skills. You will learn to design algorithms as well as develop and debug programs. Using custom open-source classes, you will write programs that access and transform images, websites, and other types of data. At the end of the course you will build a program that determines the popularity of different baby names in the US over time by analyzing comma separated value (CSV) files. After completing this course you will be able to: 1. Edit, compile, and run a Java program; 2. Use conditionals and loops in a Java program; 3. Use Java API documentation in writing programs. 4. Debug a Java program using the scientific method; 5. Write 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 multiple methods.

From the lesson

CSV Files and Basic Statistics in Java

A common format for storing tabular data (any data organized into columns and rows) is in comma separated values (CSV) files. In this module, you will learn how to analyze and manipulate data from multiple CSV data files using a powerful open-source software package: Apache Commons CSV. Using this library will empower you to solve problems that could prove too complex to solve with a spreadsheet. By the end of this module, you will be able to: (1) Use the open-source Apache Commons CSV package in your own Java programs; (2) Access data from one or many CSV files using Java; (3) Convert strings into numbers; (4) Understand how to use “null” in Java programs (when you want to represent “nothing”); (5) Devise an algorithm (and implement in Java) to answer questions about CSV data; and (6) Analyze CSV data across multiple CSV files (for example, find maximums, minimums, averages, and other simple statistical results).

Hottest Day in a Year: Comma Separated Values2:29

Converting Strings to Numbers4:27

Maximum Temperature: Developing an Algorithm5:13

Java for Nothing—null: When You Don't Have an Object4:17

Maximum Temperature: Translating into Code4:42

Maximum Temperature: Testing Code3:33

Maximum Temperature from Multiple Datasets5:51

Maximum Temperature Refactored4:07

CSVMax: Summary0:41

Meet the Instructors

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

Technically my code is done.

But I feel a little uncomfortable about the amount of duplicated code

that occurred in both of the methods that I wrote.

And I know that it was duplicated because I copied and

pasted between the two methods.

And in programming that's not a good way to create your programs because if you

have a problem in that piece of code it now appears multiple times.

And you have to try to fix it in all those different places.

So what I'd like to do is I'd like to factor out that common code and

put it in its own method, which here I've named getLargestOfTwo, so

that I can reuse that code in all of my other methods.

So the part that I copied and pasted was this if else

statement that appears both in the hottest of many days and

in, The hottest hour in a file.

So I'm gonna go ahead and cut that code from that method,

and put it into getLargestOfTwo, including, at the end,

returning the LargestSoFar so

that I have the right result.

And I don't have to make any changes to the code because, in my particular case,

I had everything named the same.

So, both of them call the current one currentRow and

the largest one largestSoFar.

And largestSoFar should remain the same unless it's null or

unless currentTemp is greater.

So in those two cases I should update largestSoFar, but

otherwise largestSoFar is the correct value.

So that's what my method is going to look like.

It's just gonna be those two.

The if and the else statement and a return of its own.

And now I can use that here to say,

largestSoFar gets

getLargestofTwo and

I'll pass it the current row and

largestSoFar.

That will do the work of my if else statement.

Store the result there, and likewise I can now copy and

paste this one line of code into hottest of many files,

and replace again that same if else with,

That one line, sorry I lost my place there for a moment, so

I get the current row from the file and I get the largest of the two.

And now let's go ahead and compile and

make sure that I didn't misspell something by not capitalizing it.

And then since I copied and pasted that, I have to fix it twice,

which is exactly what I was warning you about earlier.

And so now hopefully, since I fixed both of those, it will compile.

And now we have to go back and

test it, just to make sure that everything is correct.

So I'm gonna create a new CSV max, cuz even though I moved code around and

it shouldn't have changed the functionality,

I wanna actually make sure that that's true.

So I'm gonna test the hottest of the day and sure enough it gives 54 for

January 2nd of 2015 and I'm gonna call get hottest in many days.

And I'm gonna go back and select those two days that we've been using for

our test, and sure enough, it still thinks it was 54 degrees.

So with those tests, I feel good that the changes that I made

in terms of moving code around didn't affect the functionality.

But now I feel more confidence in my code because this large piece of code

that was duplicated, now I've taken care of it.

It only appears in one place, so

if I ever find a problem with that, I can go back and fix it just in that one place.

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