Let's install the JDK at the beginning of building the Java development environment.
First of all, https://www.oracle.com/jp/java/technologies/javase-downloads.html Look at the Java SE version from the official website and click "JDK Download" at the bottom right. Go to the download details screen and click the link "jdk-15.0.1_osx-x64_bin.dmg". Check the "License Agreement" checkbox and click "Download jdk-15.0.1_osx-x64_bin.dmg" to start the download.
Click on the downloaded file and click
Move to the installation screen and press the "Continue" button.
Next, press the install button.
Next, it was installed successfully.
After installing, check the code below in the terminal.
The installed Java version is available. So it was installed correctly.
java 15.0.1 2020-10-20 Java(TM) SE Runtime Environment (build 15.0.1+9-18) Java HotSpot(TM) 64-Bit Server VM (build 15.0.1+9-18, mixed mode, sharing)
that's all. Thank you for reading this far. I hope it will be helpful somehow.