import javax.swing.JFrame;

public class Semester {

    public static void main(String[] args) {
        window w = new window();
        w.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        w.setSize(300,100);
        w.setLocation(500,250);
        w.setVisible(true);
    }
}

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class window extends JFrame {

    private JButton me, fa;

    public window() {
        super("Semester Wrap-Up");
        setLayout(new FlowLayout());

        me = new JButton("Minimum Exam Grade");
        fa = new JButton("Final Semester Average");

        add(me);
        add(fa);

        Handler h = new Handler();
        me.addActionListener(h);
        fa.addActionListener(h);
    }

    private class Handler implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            if(e.getSource() == me) {
                MinimumExam m = new MinimumExam();
                m.setSize(300,130);
                m.setLocation(500,250);
                m.setVisible(true);
            }
            else if(e.getSource() == fa) {
                FinalAvg f = new FinalAvg();
                f.setSize(300,200);
                f.setLocation(500,250);
                f.setVisible(true);
            }
        }
    }
}

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class MinimumExam extends JFrame {

    private JLabel first, second;
    private JTextField fInput, sInput;
    private JButton calculate;

    public MinimumExam() {
        super("Minimum Exam Grade");
        setLayout(new FlowLayout());

        first = new JLabel("First Nine Weeks Average:");
        second = new JLabel("Second Nine Weeks Average:");

        fInput = new JTextField(3);
        sInput = new JTextField(3);

        calculate = new JButton("Calculate");

        add(first);
        add(fInput);
        add(second);
        add(sInput);
        add(calculate);

        Handler h = new Handler();
        calculate.addActionListener(h);
    }

    private class Handler implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            if(e.getSource() == calculate) {
                calc(fInput.getText(),sInput.getText());
            }
        }
    }

    public void calc(String f, String s) {
        try {
            int first = Integer.parseInt(f);
            int second = Integer.parseInt(s);
            double minA = (8950/15.0) - (43/15.0)*first - (42/15.0)*second;
            double minB = (7950/15.0) - (43/15.0)*first - (42/15.0)*second;
            double minC = (7450/15.0) - (43/15.0)*first - (42/15.0)*second;
            double minD = (6950/15.0) - (43/15.0)*first - (42/15.0)*second;

            JFrame results = new JFrame("Results");
            JTextArea r = new JTextArea(15,5);
            r.setEditable(false);
            r.append(String.format("%.2f to get an A\n%.2f to get a B\n%.2f to get a C\n%.2f to pass",minA,minB,minC,minD));
            results.add(r);
            results.setSize(200,100);
            results.setLocation(500,250);
            results.setVisible(true);
        } catch(NumberFormatException ex) {
            JOptionPane.showMessageDialog(null,"You must enter valid number grades.","ERROR",JOptionPane.ERROR_MESSAGE);
        }
    }
}

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class FinalAvg extends JFrame {

    private JLabel first, second, exam;
    private JTextField fIn, sIn, eIn;
    private JButton calculate;

    public FinalAvg() {
        super("Final Semester Average");
        setLayout(new FlowLayout());

        first = new JLabel("First Nine Weeks Average:");
        second = new JLabel("Second Nine Weeks Average:");
        exam = new JLabel("Semester Exam Grade:");

        fIn = new JTextField(3);
        sIn = new JTextField(3);
        eIn = new JTextField(3);

        calculate = new JButton("Calculate");

        add(first);
        add(fIn);
        add(second);
        add(sIn);
        add(exam);
        add(eIn);
        add(calculate);

        Handler h = new Handler();
        calculate.addActionListener(h);
    }

    private class Handler implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            if(e.getSource() == calculate) {
                calc(fIn.getText(),sIn.getText(),eIn.getText());
            }
        }
    }

    public void calc(String f, String s, String e) {
        try {
            int first = Integer.parseInt(f);
            int second = Integer.parseInt(s);
            int exam = Integer.parseInt(e);
            long semAvg = Math.round(.43*first + .42*second + .15*exam);

            JOptionPane.showMessageDialog(null,"Semester Average: "+semAvg,"Result",JOptionPane.PLAIN_MESSAGE);
        } catch(NumberFormatException ex) {
            JOptionPane.showMessageDialog(null,"You must enter valid number grades.","ERROR",JOptionPane.ERROR_MESSAGE);
        }
    }
}