Start to Use the Java

Enter my practice set

Into
  Everything operates here (Into.java).

public class Into{
    public static void main(String[] args) {
        System.out.println("Greeting");
    }
}

And then
  Combining multiple different classes

public class Into{
    public static void main(String[] args) {
        System.out.println("Greeting");
        System.err.println("Will it print? Yes");
        nothing();
        something();
    }
    public static int nothing(){
        int a = 0;
        System.out.print(a + " ");
        a += 1;
        return 0;
    }
    public static int something(){
        System.out.println("Watching 魔入りました！入間くん (￣▽￣)\"");
        return 0;
    }
}

Greeting
Will it print? Yes
0 Watching 魔入りました！入間くん (￣▽￣)"

At Last
  Combine different Java files

package com.Ludwig.Into;

import com.Ludwig.nothing.None;;

public class Into{
    public static void main(String[] args) {
        System.out.println("Greeting");
        System.err.println("Will it print? Yes");
        nothing();
        something();
        None.printNone();
    }
    public static int nothing(){
        int a = 0;
        System.out.print(a + " ");
        a += 1;
        return 0;
    }
    public static int something(){
        System.out.println("Watching 魔入りました！入間くん (￣▽￣)\"");
        return 0;
    }
}
        

package com.Ludwig.nothing;

public class None {
    public static void printNone() {
        System.out.println("none");
    }
}
        

Greeting
Will it print? Yes
0 Watching 魔入りました！入間くん (￣▽￣)"
none

Interlude

Don't use VSC,  please use IDE, I am very stupid.
The plugin I installed (Or just me using it in not intelligent way) isn't intelligent enough to find all the files that need to be compiled yet; I need to manually enter commands to switch directories and compile them.