一、前言

           本文内容：武汉理工大学Java语言程序设计第二次课内实验的内容，分为有按钮和无按钮。

           开发工具：IntelliJ IDEA2021.2.3

二、实验描述

1.实验描述

            根据教材关于Java GUI的介绍，编写一个具有如下布局的应用程序，要求挡在上面的文本区输入若干数据后（输入的多个数据之间以逗号分隔），并点击按钮，就可以在下面的文本框中分别显示除输入数据的和与平均数。

2.基本要求

             在完成上述要求的情况下，考虑改进该应用程序，从界面上去掉按钮，并且随着输入数据的变化，其和与平均数能够立可显示在下面的相应文本框中。

              要求考虑异常处理，使得程序能够正常运行。

三、具体实现

1.有按钮

​
  
        
        frame = new JFrame("和与平均数");
        frame.getContentPane().setFont(font);
        frame.setBounds(400,200,400,400);
        mainPanel = new JPanel();
        initComponent();
        initEvent();
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  
    
        //文本框设置
        textArea = new JTextArea();
        textArea.setPreferredSize(new Dimension(300, 100));
        textArea.setToolTipText("将输入数据用逗号分开！");
        textArea.setFont(font);
    
        JPanel textAreaPanel = new JPanel();
        textAreaPanel.setPreferredSize(new Dimension(350, 150));
        textAreaPanel.add(textArea);
        mainPanel.add(textAreaPanel, BorderLayout.NORTH);
    
        //和值显示框
        sumField = new JTextField();
        sumField.setFont(font);
        sumField.setEditable(false);
        sumField.setPreferredSize(new Dimension(300, 30));
        JLabel sumLabel = new JLabel("和值");
        JPanel sumFieldPanel = new JPanel();
        sumFieldPanel.add(sumLabel);
        sumFieldPanel.add(sumField);
    
        //平均值显示框
        averageField = new JTextField();
        averageField.setFont(font);
        averageField.setEditable(false);
        averageField.setPreferredSize(new Dimension(300, 30));
        JLabel averageLabel = new JLabel("平均值");
        JPanel averageFieldPanel = new JPanel();
        averageFieldPanel.add(averageLabel);
        averageFieldPanel.add(averageField);
    
        //计算按钮
        calculateButton = new JButton("计算");
        calculateButton.setPreferredSize(new Dimension(60, 40));
        JPanel calculatePanel = new JPanel();
        calculatePanel.add(calculateButton);
    
        JPanel centerPanel = new JPanel();
        centerPanel.add(sumFieldPanel);
        centerPanel.add(averageFieldPanel);
        centerPanel.add(calculatePanel);
    
        frame.add(mainPanel, BorderLayout.NORTH);
        frame.add(centerPanel, BorderLayout.CENTER);

​

public void inEvent(){ 
calculateButton.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseClicked(MouseEvent e) {
                if (e.getButton() == MouseEvent.BUTTON1) {
                    String numberText = textArea.getText();
                    if (numberText == null || numberText.trim().length() == 0) {
                        JOptionPane.showMessageDialog(null, "输入为空！");
                        sumField.setText(" ");
                        averageField.setText(" ");
                    } else {
                        String[] numString = numberText.split(";");
                        double[] numDouble = stringToTypeDouble(numString);
                        double sumNumber = sumCalculate(numDouble);
                        double averNumber = averCalculate(numDouble);
                        sumField.setText(String.valueOf(sumNumber));
                        averageField.setText(String.valueOf(averNumber));
                    }
                }
            }
        });
}

private double[] stringToTypeDouble(String[] string ) {
        if(string == null || string.length==0){
            return null;
        }else{
            double[]arrDouble = new double[string.length];
            try{
                for(int i = 0; i<string.length;i++) {
                    String str = string[i].trim();
                    arrDouble[i] = Double.parseDouble(str);
                }
            }catch (NumberFormatException e){
                e.printStackTrace();
                arrDouble = null;
                JOptionPane.showMessageDialog(null,"输入的数据类型错误！");
            }catch (InputMismatchException e){
                e.printStackTrace();
                arrDouble = null;
                JOptionPane.showMessageDialog(null,"输入的数据格式错误！");
            }
            return arrDouble;
        }
    }

  /**
     * 计算和值
     */
    private double sumCalculate(double[] arrDouble){
        double sumNum = 0;
        if(arrDouble == null || arrDouble.length == 0){
            return sumNum;
        }else{
            for (double v : arrDouble) {
                sumNum = sumNum + v;
            }
            return Double.parseDouble(new DecimalFormat("#.000").format(sumNum));
        }
    }
    
    /**
     * 计算平均值
     */
    private double averCalculate(double[]arrDouble) {
        double averNum = 0;
        if(arrDouble == null || arrDouble.length == 0){
            return averNum;
        }else{
            averNum = sumCalculate(arrDouble)/arrDouble.length;
            return Double.parseDouble(new DecimalFormat("#.000").format(averNum));
        }
    }

2.无按钮

        无按钮的界面设计只需将“计算”按钮删除即可。

 /**
     * 键盘输入处理
     */
    private void initEvent() {
        textArea.getDocument().addDocumentListener(new DocumentListener() {
            @Override
            public void insertUpdate(DocumentEvent e) {
                updateTextArea();
            }
    
            @Override
            public void removeUpdate(DocumentEvent e) {
                updateTextArea();
            }
    
            @Override
            public void changedUpdate(DocumentEvent e) {
                updateTextArea();
            }
        });
    }

 private void updateTextArea() {
        String numberText = textArea.getText();
        if( numberText.trim().length() == 0){
            JOptionPane.showMessageDialog(null,"输入为空！！！");
            sumField.setText(" ");
            averageField.setText(" ");
        }else{
            String[] numString = numberText.split(";");
            double[] numDouble = stringToTypeDouble(numString);
            double sumNumber = sumCalculate(numDouble);
            double averNumber = averCalculate(numDouble);
            sumField.setText(String.valueOf(sumNumber));
            averageField.setText(String.valueOf(averNumber));
        }
    }
    

private double[] stringToTypeDouble(String[] string) {
        if(string == null || string.length==0){
            return null;
        }else {
            double[] arrDouble = new double[string.length];
            try {
                for (int i = 0; i < string.length; i++) {
                    String str = string[i].trim();
                    arrDouble[i] = Double.parseDouble(str);
                }
            } catch (NumberFormatException e) {
                e.printStackTrace();
                arrDouble = null;
                JOptionPane.showMessageDialog(null, "输入的数据类型错误！");
            } catch (InputMismatchException e) {
                e.printStackTrace();
                arrDouble = null;
                JOptionPane.showMessageDialog(null, "输入的数据格式错误！");
            }
            return arrDouble;
        }
    }
    

 private double sumCalculate(double[] arrDouble) {
        double sumNum = 0;
        if(arrDouble == null || arrDouble.length == 0){
            return sumNum;
        }else{
            for (double v : arrDouble) {
                sumNum = sumNum + v;
            }
            return Double.parseDouble(new DecimalFormat("#.000").format(sumNum));
        }
    }
    
    private double averCalculate(double[] arrDouble) {
        double averNum = 0;
        if(arrDouble == null || arrDouble.length == 0){
            return averNum;
        }else{
            averNum = sumCalculate(arrDouble)/arrDouble.length;
            return Double.parseDouble(new DecimalFormat("#.000").format(averNum));
        }
    }