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I can't use java on mac

I'm a programming beginner studying Java on mac. ..
A native app called Progate? While watching on iPhone, I am studying Java by actually typing the code on the PC with vscode.
About three days ago, there was an update called macOS Big Sur.
Immediately before updating, I was studying Java while typing the code with vscode, and even if I debugged it, it gave me normal values.
However, as soon as I updated it during that time, the code that was working a while ago became full of errors, and it stopped working at all.
It may be a mistake, but when I asked Apple's customer support, it seems that they did not receive the same reports and consultations as I did, and the person in charge said that I could not consider it at all.

I'm looking every day to see if anyone is experiencing the same phenomenon on the internet, but I can't find it, and I'm sure my settings are wrong, but I have no idea what's wrong. ..

You may be too inexperienced in programming to ask a question here, but I would like to ask you if you can find a clue to a solution.
Since this is my first time using this site, I think there are many points that are difficult to understand, and it will be a long sentence, but thank you.

-The type java.lang.Object cannot be resolved. It is indirectly referenced from required .class files Java (16777540) [1, 1]
-Implicit super constructor Object () is undefined for default constructor. Must define an explicit constructor Java (134217876) [1, 7]
-String cannot be resolved to a type Java (16777218) [2, 29]
-System cannot be resolved Java (570425394) [3, 9] [4, 9] [6, 9]
The above four sentences appear next to the cross.

The following sentences are in △! It comes out following the mark of.
-Comparing identical expressions Java (536871123) [3, 28] [4, 28] [5, 22]

The last one is the file mark? Appears under the display like and the display java_7bcfe822
The project was not built since its build path is incomplete. Cannot find the class file for java.lang.Object. Fix the build path then try building this project Java (0) [1, 1]

Is displayed and the conditional expression is not calculated. As a precaution, I have listed up to the displayed part, so I'm sorry if it is difficult to understand line breaks etc.

Corresponding source code

Java

class Main2 {
public static void main (String [] args) {
System.out.println (12/4 == 3);
System.out.println (12/4! = 3);
boolean bool = 3 * 9 == 27;
System.out.println (bool);
}
}

I couldn't hit it like the actual code like everyone else. I'm sorry.

What I tried

Go to the Oracle site and reinstall the latest version of Java
Ask Apple Customer Support by phone
Java installation and update via Homebrew in terminal
And so on.
Since I have little knowledge about PCs in the first place, I think that it will be more complicated if I play with it strangely, so I try not to touch it too much, and I type a code in a terminal etc. I saw on the net etc. and pass it through the path etc. I can't go to the screen that the person who explains whether the method is different.

Supplement

Macbook air Retina 13 inch 2018 model
macOS Big Sur version 11.0.1
Java is displayed as Java SE 15