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) **  image.png

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.

--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
Column 1
What is jdk and why do I need to install jdk?
Column 2
What is an IDE and why do I need to install an IDE?


--jdk installation (★ TODO)

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

Column 3
About jdk type and sorting method

--Install sts (eclipse) (★ TODO)

Column 4
About the main IDE types

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. image.png

STS is running ... image.png

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. image.png   After a while, you will see a screen like this. This completes STS startup. image.png

-** 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 image.png

Click "New" in the menu image.png

Click "Java project" in the menu image.png

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

-** 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

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