explain the close() method in Java in Layman's terms

Question

I went through a java tutorial that allowed me to create a text file and write the words,"20 Bruce Wayne" in it. The last method that is called in the main class is named closeFile() that "closes" the text file after it is created.

Why does the file need to be "closed" if I didn't really open it? By "open", I mean the Notepad editor(not the IDE I'm using) pops up with the words "20 Bruce Wayne". Please answer my question in layman's terms.

Main.java:

class apple {
    public static void main(String[] args)
    {
        createfile g = new createfile();
        g.openFile();
        g.addRecords();
        g.closeFile();
    }
}

createfile.java

public class createfile {
    private Formatter x;

    public void openFile(){
        try{
            x = new Formatter("supermanvsbatman.txt");
        }
        catch(Exception e){
            System.out.println("you have an error");
        }
    }
    public void addRecords(){
        x.format("%s%s%s","20 ", "Bruce ", "Wayne ");
    }
    public void closeFile(){
        x.close();
    }
}

Answer 1

When a file is "opened," the OS marks the file as locked, generally so it can't be deleted by other processes while it's being used. x.close() undoes the lock, allowing the OS and other processes to do what it wishes with the file.