自己写的java学生成绩评定小程序

import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DecimalFormat;

import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.border.TitledBorder;

public class StudentGrades extends JFrame{
 
 
 private static final long serialVersionUID = 1L;
 
 private JLabel test1Label;
 private JLabel test2Label;
 private JLabel test3Label;
 private JLabel studentNameLabel;
 private JLabel averageLabel;
 
 private JTextField test1TextField;
 private JTextField test2TextField;
 private JTextField test3TextField;
 private JTextField studentNameTextField;
 private JTextField averageTextField;
 
 private JTextArea studentScoreTextArea;
 
 private JButton submitGradesJButton;
 
 private TitledBorder inputTitledBorder;
 private TitledBorder averageScoreTitledBorder;
 private JRadioButton numericJRadioButton;
 private JRadioButton letterJRadioButton;
 
 private JPanel inputScoreJPanel;
 private JPanel averageScoreJPanel;

 private final int MAXIMUM_STUDENTS = 10;
 private final int NUMBER_OF_TESTS = 3;
 private int classCounter = 0;
 private double studentGrades[][] = new double[MAXIMUM_STUDENTS][NUMBER_OF_TESTS+1];
 private String[] strudentNames = new String[MAXIMUM_STUDENTS];
 private double totalGrades = 0;
 private DecimalFormat gradesFormat;
 
 public JPanel getAverageScoreJPanel() {
  averageScoreJPanel = new JPanel();
  
  studentScoreTextArea = new JTextArea();
  studentScoreTextArea.setBounds(12,20,425,200);
  studentScoreTextArea.setText("Name\tTest 1\tTest 2\tTest 3\tAverage\n");
  averageScoreJPanel.add(studentScoreTextArea);
  
  averageScoreTitledBorder = new TitledBorder("Average of each student");
  averageScoreJPanel.setBorder(averageScoreTitledBorder);  
  averageScoreJPanel.setBounds(230,20,445,230);
  averageScoreJPanel.setLayout(null);
  return averageScoreJPanel;
 }

 public JPanel getInputScoreJPanel() {
  studentNameLabel = new JLabel("student name:");
  studentNameLabel.setBounds(10,30,90,25);
  
  test1Label = new JLabel("test1:");
  test1Label.setBounds(10,70,80,25);
  
  test2Label = new JLabel("test2:");
  test2Label.setBounds(10,110,80,25);
  
  test3Label = new JLabel("test3:");
  test3Label.setBounds(10,140,80,25);
  
  studentNameTextField = new JTextField();
  studentNameTextField.setBounds(120,30,80,25);
  
  test1TextField = new JTextField();
  test1TextField.setBounds(120,70,80,25);
  
  test2TextField = new JTextField();
  test2TextField.setBounds(120,110,80,25);
  
  test3TextField = new JTextField();
  test3TextField.setBounds(120,140,80,25);
  
  submitGradesJButton = new JButton();
  submitGradesJButton.setText("Student Grades");
  submitGradesJButton.setBounds(80,180,130,25);
  submitGradesJButton.addActionListener(new ActionListener(){

   @Override
   public void actionPerformed(ActionEvent e) {
    // TODO Auto-generated method stub
    submitGradesJButtonactionPerformed(e);
   }   
  });
  
  inputTitledBorder = new TitledBorder("input Grades");
  inputScoreJPanel = new JPanel();
  inputScoreJPanel.setBounds(5,20,245,230);
  inputScoreJPanel.setLayout(null);
  
  inputScoreJPanel.add(studentNameLabel);
  inputScoreJPanel.add(test1Label);
  inputScoreJPanel.add(test2Label);
  inputScoreJPanel.add(test3Label);
  inputScoreJPanel.add(studentNameTextField);
  inputScoreJPanel.add(test1TextField);
  inputScoreJPanel.add(test2TextField);
  inputScoreJPanel.add(test3TextField);
  inputScoreJPanel.setBorder(inputTitledBorder);
  inputScoreJPanel.add(submitGradesJButton);
  return inputScoreJPanel;
 }

 public StudentGrades(){
  createGUI();
 }
 
 private void createGUI(){
  gradesFormat = new DecimalFormat("0.00");
  
  Container contentPane = getContentPane();
  contentPane.setLayout(null);
  
  ButtonGroup buttonGroup = new ButtonGroup();
  numericJRadioButton = new JRadioButton();
  numericJRadioButton.setText("numeric");
  numericJRadioButton.setBounds(50,250,80,25);
  numericJRadioButton.setSelected(true);
  numericJRadioButton.addActionListener(new ActionListener(){

   @Override
   public void actionPerformed(ActionEvent e) {
    // TODO Auto-generated method stub
    numericJRadioButtonactionPerformed(e);
   }
   
  });
  
  letterJRadioButton = new JRadioButton();
  letterJRadioButton.setText("letter");
  letterJRadioButton.setBounds(140,250,80,25);
  letterJRadioButton.setSelected(false);
  letterJRadioButton.addActionListener(new ActionListener(){

   @Override
   public void actionPerformed(ActionEvent e) {
    // TODO Auto-generated method stub
    letterJRadioButtonactionPerformed(e);
   }   
  });
  
  buttonGroup.add(letterJRadioButton);
  buttonGroup.add(numericJRadioButton);
  
  averageLabel = new JLabel();
  averageLabel.setText("class average:");
  averageLabel.setBounds(450,250,100,25);
  averageLabel.setHorizontalAlignment((int) numericJRadioButton.TOP_ALIGNMENT);
  
  averageTextField = new JTextField();
  averageTextField.setBounds(555,250,80,25);
  averageTextField.setEditable(false);
  
  setBounds(300,250,690,330);
  contentPane.add(getInputScoreJPanel());
  contentPane.add(getAverageScoreJPanel());
  contentPane.add(numericJRadioButton);
  contentPane.add(letterJRadioButton);
  contentPane.add(averageLabel);
  contentPane.add(averageTextField);
  setTitle("Average Student Grades");
  setVisible(true);
  setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
 }
 
 private void numericJRadioButtonactionPerformed(ActionEvent e) {
  // TODO Auto-generated method stub
  studentScoreTextArea.setText("Name\tTest 1\tTest 2\tTest 3\tAverage\n");
  for(int i=0; i
   String str = strudentNames[i]+"\t"+studentGrades[i][0]+"\t"
     +studentGrades[i][1]+"\t"+studentGrades[i][2]+"\t"
     +gradesFormat.format(studentGrades[i][3])+"\n";
   if(strudentNames[i] != null){
    System.out.println(str);
   }
   studentScoreTextArea.append(str);
   String t =""+ totalGrades/classCounter;
   averageTextField.setText(t);
  }
 }

 private void letterJRadioButtonactionPerformed(ActionEvent e) {
  // TODO Auto-generated method stub
  studentScoreTextArea.setText("Name\tTest 1\tTest 2\tTest 3\tAverage\n");
  for(int i=0; i
   String str = strudentNames[i]+"\t"+gradesLevel(studentGrades[i][0])+"\t"
     +gradesLevel(studentGrades[i][1])+"\t"
     +gradesLevel(studentGrades[i][2])+"\t"
     +gradesLevel(studentGrades[i][3])+"\n";
   if(strudentNames[i] != null){
    System.out.println(str);
   }
   studentScoreTextArea.append(str);
   String t =""+ gradesLevel(totalGrades/classCounter);
   averageTextField.setText(t);
  }
 }
 

 private void submitGradesJButtonactionPerformed(ActionEvent e) {
  // TODO Auto-generated method stub
  
  String strName = studentNameTextField.getText();
  String strTest1 = test1TextField.getText();
  String strTest2 = test2TextField.getText();
  String strTest3 = test3TextField.getText();
  double test1Grade = Double.valueOf(strTest1);
  double test2Grade = Double.valueOf(strTest2);
  double test3Grade = Double.valueOf(strTest3);
  double averageGrade = (test1Grade+test2Grade+test3Grade)/NUMBER_OF_TESTS;
  
  strudentNames[classCounter] = strName;
  studentGrades[classCounter][0] = test1Grade;
  studentGrades[classCounter][1] = test2Grade;
  studentGrades[classCounter][2] = test3Grade;
  studentGrades[classCounter][3] = averageGrade;

//  String strAverage = ""+averageGrade;
  String str = strName+"\t"+strTest1+"\t"+strTest2
    +"\t"+strTest3+"\t"+gradesFormat.format(averageGrade)+"\n";
  studentScoreTextArea.append(str);
  totalGrades += averageGrade;
  classCounter++;
//  String t =""+ totalGrades/classCounter;
  averageTextField.setText(gradesFormat.format(totalGrades/classCounter));
  
  if(classCounter == MAXIMUM_STUDENTS){
   submitGradesJButton.setEnabled(false);
  }
 }
 
 private char gradesLevel(double grade){
  if(grade>89 && grade<=100){
   return 'A';
  }
  if(grade>79 && grade<90){
   return 'B';
  }
  if(grade>69 && grade<80){
   return 'C';
  }
  if(grade>59 && grade<70){
   return 'D';
  }
  if(grade<60){
   return 'E';
  }
  return 'F';
 }
 
 public static void main(String args[]){
  new StudentGrades();
 }
}