Variables

Loading...

From the course by Duke University

Java Programming: Solving Problems with Software

1974 ratings

Duke University

Java Programming: Solving Problems with Software

1974 ratings

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

Fundamental Java Syntax and Semantics

In this module, you will learn to write and run your first Java programs, including one program that prints “Hello!” in various countries’ languages and another where you will analyze the perimeters and other information of shapes. To accomplish these tasks, you will learn the basics of Java syntax and how to design stepwise solutions with programs. By the end of this module, you will be able to: (1) Download and run BlueJ, the Java programming environment for this course; (2) Access the documentation for the Java libraries specially designed for this course; (3) Edit, compile, and run a Java program; (4) Construct methods, variables, if else statements, and for each loops in Java; and (5) Use Iterables (like DirectoryResource) to run a program that iterates over multiples lines in a document or webpage or multiple files in a directory.

Shapes: Collections of Points2:29

Why Semantics: Motivation to Read Code1:11

Mathematical Operators2:24

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

Hello. We're going to start learning to execute code with

the most basic statements in Java and build up to more complex statements from there.

Here, we have two variable declarations.

One for an int called X,

and one for an int called Y.

If we execute these statements as is,

we will create boxes labeled X and Y to

hold the values we eventually decide to put in these variables.

But in this example,

we have not explicitly provided any initial values.

In some languages such as C,

no default value is ever provided when you declare a variable.

Meaning, you get undefined behavior if you use an uninitialized variable.

This is such a common and significant problem that Java provides

two solutions: an initial default value of zero is given to instance variables,

or an explicit error is given for using a local variable before initializing it.

We will see these different types of variables in upcoming videos.

Now, let us look at another example which

initializes the variables when they are declared.

Here, the first statement declares an int called X. Executing

it makes a box for X and immediately assigns the value 4 to X.

We show this by putting 4 in the box for X. Executing the next line,

both creates a box for Y and puts the value 6 in that box.

Combining the declaration and initialization of

your variables into the same statement won't pose a problem in any language.

And anyone reading your code knows exactly what you meant for the code to do.

So this is a good habit to get into.

Of course, variables are only useful if you make use of the value that they have.

Here, the first code declares X and initializes it to 4.

Next, Y declares and initializes it to X + 2.

To perform this statement we must

evaluate the expression on the right hand side of the equal sign.

X is 4, so X + 2 is 4 + 2 or 6.

We show this by creating a box for Y and putting 6 into it.

The last statement creates a variable Z and initializes it to Y - X.

So you would take the value of Z, which is 6,

and the value of X, which is 4,

and subtracts them to get 2.

You would then create a box for Z and initialize it to 2.

Great. Now, you know how to execute code with

variable declarations and assignment statements.

Explore our Catalog

Join for free and get personalized recommendations, updates and offers.

Coursera provides universal access to the world’s best education, partnering with top universities and organizations to offer courses online.

© 2018 Coursera Inc. All rights reserved.

Download on the App Store

Get it on Google Play