gpa计算器

// Main.java

import javax.swing.*;

public class Main {
    public static void main(String[] agrs) {
        MyFrame frame = new MyFrame("gpa");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(350,750);
        frame.setVisible(true);
    }
}

// MyFrame.java
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Calendar;

public class MyFrame extends JFrame {
    final int num = 15;
    JTextField[] subjectName = new JTextField[num];
    JTextField[] subjectCredit = new JTextField[num];
    JComboBox<String>[] subjectGrade = new JComboBox[num];

    public MyFrame(String name) {
        super(name);
        Container cta = getContentPane();
        cta.setLayout(new FlowLayout());
        for(int i=0;i < num;i++) {
            subjectGrade[i] = new JComboBox<>();
            subjectGrade[i].addItem("A+");
            subjectGrade[i].addItem("A");
            subjectGrade[i].addItem("B+");
            subjectGrade[i].addItem("B");
            subjectGrade[i].addItem("C+");
            subjectGrade[i].addItem("C");
            subjectGrade[i].addItem("D");
            subjectGrade[i].addItem("F");
            subjectGrade[i].setToolTipText("请选择等级");

            subjectName[i] = new JTextField(16);
            subjectName[i].setToolTipText("请输入科目名" + (i+1));

            subjectCredit[i] = new JTextField(5);
            subjectCredit[i].setToolTipText("请输入课程学分");
        }

        for(int i=0;i < num;i++) {
            cta.add(subjectName[i]);
            cta.add(subjectCredit[i]);
            cta.add(subjectGrade[i]);
        }

        JButton jb = new JButton("确定");
        cta.add(jb);
        jb.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                Calculate();
            }
        });
    }

    public void Calculate() {
        double totalCredit = 0;
        double totalGpa = 0;
        int i = 0;
        for(i=0;i < num;i++) {
            if(subjectName[i].getText().equals("")) {
                break;
            }
            String str = (String)subjectGrade[i].getSelectedItem();
            if(str.equals("A+")) {
                totalGpa += 4.5 * Double.parseDouble("" + subjectCredit[i].getText());
            } else if(str.equals("A")) {
                totalGpa += 4.0 * Double.parseDouble("" + subjectCredit[i].getText());
            } else if(str.equals("B+")) {
                totalGpa += 3.5 * Double.parseDouble("" + subjectCredit[i].getText());
            } else if(str.equals("B")) {
                totalGpa += 3.0 * Double.parseDouble("" + subjectCredit[i].getText());
            } else if(str.equals("C+")) {
                totalGpa += 2.5 * Double.parseDouble("" + subjectCredit[i].getText());
            } else if(str.equals("C")) {
                totalGpa += 2.0 * Double.parseDouble("" + subjectCredit[i].getText());
            } else if(str.equals("D")) {
                totalGpa += 1.0 * Double.parseDouble("" + subjectCredit[i].getText());
            } else {
                totalGpa += 0.0 * Double.parseDouble("" + subjectCredit[i].getText());
            }
            totalCredit += Double.parseDouble("" + subjectCredit[i].getText());
        }
        String out = "";
        out += "本学期一共修了" + (i) + "门科目。\n";
        out += "平均绩点为：" + (totalGpa/totalCredit);
        JOptionPane.showMessageDialog(this,out);
    }
}