Introduction

[github-learning-lab[bot]]

Java Course

Java is a popular programming language for several main reasons:

• It workes on many different platforms.
• It's easy to learn and open source.
• It's fast and powerful.

Java is considered an Object Oriented programming language, making it easy to encapsulate data (and methods) in a class. A class is like a blue-print that contains all the properties that will be inherited by the objects created by it. This makes it easy to organize and re-use blocks of code.

Java is also a compiled language, meaning that it needs to be translated into machine readable code before it can run.

GitHub Learning Lab Instructions

This is an interactive course, where you will be prompted to do something to finish each step.

If it takes more than a few seconds for a response, try refreshing your browser.

Add a comment to this issue with the letter that answers this question.

Which of the following is false about Java?

a. Java is an Object Oriented programming language b. Java is a scripting language, read only in the browser c. Java files need to be compiled before you can run them

[wcd-0306-2211]

b

[github-learning-lab[bot]]

Correct! That answer is describing JavaScript (which is entirely different than Java).

Prepare your environment

Before we can start writing Java, we need to make sure you have your environment set up. You just need a few things (some of which you might already have!)

• [x] Check if Java is installed and set path
• [x] Download a text editor
• [x] Clone your course repository using git

Check that Java is installed

Your machine may already have Java, or you might need to install it. To find out, go to your command line terminal and type:

java -version

Then type:

javac -version

If you see your Java version displayed for each of these, you're all set!

Otherwise, you'll need to download Java for your operating system.

The next step is to set the java file path by developing a new environmental variable. Go to the link above for instructions on how to find and set the path for Java. (if you already have a path variable, you can add a ; to the end and include the next path afterwards).

When you make a new environmental variable, you need to close and re-open your terminal. Do this now, then type these lines to make sure the path was set correctly.

java -version javac -version

You should see a version for each of these if it was correctly installed.

Download a text editor

Make sure you have a text editor installed before proceeding (such as Atom, Sublime Text, or Notepad++).

Clone course repository

You will be storing the code for this project in this repository. Before we go any further, clone your template project into the directory you want to store your code locally in, using git:git clone https://github.com/wcd-0306-2211/java-course.git

To test that your project is set up correctly, navigate into the folder you cloned and run these commands:

javac custom_order.java

java custom_order

If everything was set up correctly, you should see "Hello World!" printed in your command terminal. We'll describe what we just did in the next step.

When you have finished these steps, leave a comment for the next step

[github-learning-lab[bot]]

Compiling vs Running Code

The first command we entered javac custom_order.java will create a 'class' file, which is machine-readable code. The class file may be hidden on your text editor, since you should never directly edit this file. You can see it by typing ls into the terminal. When we ran the java custom_order command, we told the computer to read that class file. Therefore, we need to re-compile our code each time we make changes that we want to run.

Open the custom_order.java file in your text editor to view the code before it is compiled. We will be editing this code to create a Java Cake & Cupcake Shop ordering system!

Before you continue, is the following statement is true or false?

You need to re-compile your code each time you want to test edits to your java file.

[github-learning-lab[bot]]

Sorry, that is not the right answer. 😢
Try again! 😄

[github-learning-lab[bot]]

Sorry, that is not the right answer. 😢
Try again! 😄

[wcd-0306-2211]

yes

[github-learning-lab[bot]]

Sorry, that is not the right answer. 😢
Try again! 😄

[wcd-0306-2211]

编译与运行代码

我们输入的第一个命令将创建一个"类"文件，这是机器可读代码。类文件可能隐藏在文本编辑器上，因为您不应该直接编辑此文件。您可以通过键入终端来查看它。当我们运行命令时，我们告诉计算机读取该类文件。因此，每次我们进行要运行的更改时，都需要重新编译代码。javac custom_order.java``ls``java custom_order

打开文本编辑器中的custom_order.java文件，以便在代码编译之前查看代码。我们将编辑此代码，以创建一个 Java 蛋糕和蛋糕店订购系统！

在继续之前，以下陈述是真还是假？

每次要测试对 java 文件的编辑时，您都需要重新编译代码。

[github-learning-lab[bot]]

Sorry, that is not the right answer. 😢
Try again! 😄