Need code explanation

Question

//I have the following code I am trying to understand, mainly how its calling the other classes. Any explanation would be great. Thanks Rick
import javax.swing.*;
import java.util.*;
//I know this is the class after compiled...
public class Assignment4Driver
     //I am trying to understant how this calling works
     public static void main(String[] args)
          ReadInput input2 = new ReadInput();
          int gradeCount = input2.readInput();
          GetGrade grade2 = new GetGrade();
          char grade = grade2.getGrade(gradeCount);     
          WriteOutput output2 = new WriteOutput();
          output2.writeOutput (gradeCount, grade);
//ReadInput.java file
public class ReadInput
     public int readInput()
          int gradeCount = 0;
          int counter = 0;
          while (counter < 5)
               String gradeString = JOptionPane.showInputDialog("Enter grade from 0 to 20:");
               gradeCount = gradeCount + Integer.parseInt(gradeString);
               counter++;
          return gradeCount;
//Get Grade.java file
public class GetGrade
     public char getGrade(int gradeCount)
          char grade;
          if (gradeCount >= 90) grade = 'A';
          else if (gradeCount >= 80) grade = 'B';
          else if (gradeCount >= 70) grade = 'C';
          else if (gradeCount >= 60) grade = 'D';
          else grade = 'F';
          return grade;
import javax.swing.*;
import java.util.*;
Here is the WriteOutput.java file
public class WriteOutput
     public void writeOutput(int gradeCount, char grade)
          JOptionPane.showMessageDialog(null, "The total points awarded is " + gradeCount + ",\n"
                    + "which makes your final grade a " + grade);
//Thanks a bunch.

Answer 1

Basically I included four files and want to know about this.
I think it looks like you are calling your class ReadInput, then it looks like you are assigning whatever value is there when you first call it to "input2", then you are saying that the "new" value is equivalent to input2 after the ReadInput file is read.
ReadInput input2 = new ReadInput();
after that you are saying the the variable gradeCount from the ReadInput file is equal to the input2.readInput, but I can't explain the input2.readInput below.
int gradeCount = input2.readInput();
portion of the code....
I am not a big coder, and have been only working with one file at a time. I am trying to understand how you can have one class and call another class. I will study some more and see if I can post a question that makes more sense to you. I will see if I can access this site from work so I can keep looking at this thread.