java basic knowledge memo

It is a compilation based on personal experience at the development site, so please read it for reference only.

What is java

If you search for "what is java" on google etc., you will find a lot of explanations. In short, java is one of many "programming languages". In the first place, a programming language is a language that can talk to a computer. Of course, even if I write Japanese, I can't understand it on a computer. You can give commands to your computer and get answers from your computer in words written in a programming language.

** I hope there is a more beautiful picture here. .. .. (★ TODO) ** 　

What are you good at with java?

Well, there are various things, but the typical one is to create an application for an Android smartphone, Build a website ... 　 Please search for details: * java good *

Let's get started with java

There are some basic conditions for writing java.

• computer Of course, the higher the Svek, the better, but 4G or more of memory is desirable.

--Internet connection At least when building the first environment, an internet connection is required. Because the installation materials need to be downloaded from the internet

--Java writing flow

1. Java environment construction ・ Install Jdk ・ IDE installation
2. Write Java Code
3. Execute Java Code

Environment

--jdk installation (★ TODO)

Search: * jdk installation windows * Search: * jdk installation mac *

--Install sts (eclipse) (★ TODO)

Let's write Java Code!

Below is an image of writing java code in Spring Tool Suite (STS for short).

-** Start STEP1 STS **

Double-click the "STS-Shortcut" icon on your computer to start STS.

STS is running ...

Specify the directory where you want to save the files you are working on. You can specify any place you like. If you're not particular about it, leave it alone and click the Launch button. 　 After a while, you will see a screen like this. This completes STS startup.

-** STEP2 Create java project **

wait a moment. What is a java project? A java project is a collection of several Java programs as a function or application. I can't understand the concept right away, and I can gradually get used to it, so when creating a java code, just remember that you need to create a java project first, instead of writing the java code suddenly. Let's go.

Click the "file" menu on the STS screen

Click "New" in the menu

Click "Java project" in the menu

Enter a name of your choice on the "New Java Project" screen and click "Finish" 　 You can see the created projet in the upper left of the STS screen. This completes the java project creation.

-** STEP3 Create a file to store java code **

Since java code is written in class units, in technical terms, a java code file is called a class file. What is a class? 　★ＴＯＤＯ

package sample;

public class Main {

	public static void main(String[] args) {
		System.out.println("Hello World!");
	}

}

Let's execute java code!

Java Code basic configuration

--Package --Class --Method --Variables

It's still on the way. I will edit it again if I have time. : fist:

Basic syntax of java Code

• loop --Condition judgment --Processing interruption --Abnormal interruption