java - 尝试压缩转换程序

Question

我目前是一名高中生，正在本地大学攻读 DE 类(class)。我正在学习 Java 类(class)并正在从事一个项目。

我仍然是一个初学者，正如您可能在我的代码中看到的那样，并且正在尝试找到压缩我的代码的方法，以便我可以尝试添加更多内容。如果您能帮助我，我将不胜感激!

该程序是不同长度单位的转换程序。我自学了用于此目的的组合框的基础知识，尽管我对此不是很熟悉。

我也不明白为什么转换按钮会延伸这么远。最后，我需要有一个复选框，并且由于我实在想不出它的其他用途，因此我将其放入代码中，并具有您在代码中看到的效果。

注意:只是说；不要让它太复杂，我需要理解它，因为我必须解释程序中做了什么

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

public class Converter extends JFrame {

public static void main(String[] args) {
    Converter myFrame = new Converter();
}

private JPanel myP1, myP2, myP3,myP4,myP5;
private JLabel myMessageLabel,myMessageLabel2,myMessageLabel3;
private JButton myButton;
private JComboBox myBox1,myBox2;
private JTextField myText;
private JCheckBox myCheck;

String combo1, combo2;
double inputNumber, convertedNumber;
char check;

public Converter()  {
        //Dimensions of Frame
        final int W_WIDTH = 450;
        final int W_HEIGHT = 200;

        //Title of Window
        setTitle("Unit Converter");
        //Size is set
        setSize(W_WIDTH, W_HEIGHT);
        //Close operation
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        //Set layout of frame
        setLayout(new BorderLayout());
        //Building and adding panels
        buildPanel1();
        add(myP1, BorderLayout.NORTH);
        buildPanel2();
        add(myP2, BorderLayout.CENTER);
        buildPanel3();
        buildPanel4();
        add(myP4, BorderLayout.SOUTH);
        buildPanel5();
        myP2.add(myP5);
        //Making the frame visible on the screen
        setVisible(true);

}


private void buildPanel1() {
    myMessageLabel = new JLabel("Welcome to the Master Creators Unit Converter!");
    myP1 = new JPanel();

    myP1.add(myMessageLabel);

}

private void buildPanel2() {
    //First Combo Box
    String[] units = { " ","Miles", "Feet", "Kilometers", "Meters" };
    myP2 = new JPanel();
    myBox1 = new JComboBox(units);
    myBox1.addActionListener(new ComboBoxListener1());
    myP2.add(myBox1);
}

private void buildPanel3() {
    //Entering the value to be converted and check box
    myP3 = new JPanel();
    myMessageLabel3 = new JLabel("Enter a value:");
    myText = new JTextField(10);
    myCheck = new JCheckBox("Keep checked to convert!");
    myCheck.addItemListener(new CheckBoxListener());

    myP3.add(myMessageLabel3);
    myP3.add(myText);
    myP3.add(myCheck);
}

private void buildPanel4() {
    //Button to convert
    myButton = new JButton("Convert");
    myButton.addActionListener(new myButtonListener());
    myP4 = new JPanel();
    myP4.setLayout(new GridLayout(2,1));
    myP4.add(myP3);
    myP4.add(myButton);

}
private void buildPanel5() {
    //Second Combo Box
    String[] units = { " ","Miles", "Feet", "Kilometers", "Meters" };
    myP5 = new JPanel();
    myMessageLabel2 = new JLabel("to");
    myBox2 = new JComboBox(units);
    myBox2.addActionListener(new ComboBoxListener2());

    myP5.add(myMessageLabel2);
    myP5.add(myBox2);

}

private class ComboBoxListener1 implements ActionListener {
    public void actionPerformed (ActionEvent e) {
        //Giving values to the different selections in the combo box
        String selection = (String) myBox1.getSelectedItem();
        if (selection.equals("Miles")) {
            combo1 = "a";
        }
        else if (selection.equals("Feet")) {
            combo1 = "b";
        }
        else if (selection.equals("Kilometers")) {
            combo1 = "c";
        }
        else if (selection.equals("Meters")) {
            combo1 = "d";
        }
        else {
            combo1 = "z";
        }
    }
}

private class ComboBoxListener2 implements ActionListener {
    public void actionPerformed (ActionEvent e) {
        //Giving values to the different selections in the combo box
        String selection = (String) myBox2.getSelectedItem();
        if (selection.equals("Miles")) {
            combo2 = "a";
        }
        else if (selection.equals("Feet")) {
            combo2 = "b";
        }
        else if (selection.equals("Kilometers")) {
            combo2 = "c";
        }
        else if (selection.equals("Meters")) {
            combo2 = "d";
        }
        else {
            combo2 = "z";
        }
    }
}
private class myButtonListener implements ActionListener {
    public void actionPerformed(ActionEvent e) {
        String input;
        //Obtains value entered by user and converts to double
        input = myText.getText();
        inputNumber = Double.parseDouble(input);
        //Checks if the check box is checked before continuing
        if(check == 'y') {
        //Converts the value from the selected unit to the unit to convert to
        if(combo1.equals(combo2)) {
            JOptionPane.showMessageDialog(null, inputNumber);
        }
        else if (combo1 == "a" && combo2 == "b") {
            convertedNumber = inputNumber * 5280;
            JOptionPane.showMessageDialog(null, convertedNumber + " feet");
        }
        else if (combo1 == "a" && combo2 == "c") {
            convertedNumber = inputNumber * 1.60934;
            JOptionPane.showMessageDialog(null, convertedNumber + " kilometers");
        }
        else if (combo1 == "a" && combo2 == "d") {
            convertedNumber = inputNumber * 1609.34;
            JOptionPane.showMessageDialog(null, convertedNumber + " meters");
        }
        else if (combo1 == "b" && combo2 == "a") {
            convertedNumber = inputNumber * 0.000189394;
            JOptionPane.showMessageDialog(null, convertedNumber + " miles");
        }
        else if (combo1 == "b" && combo2 == "c") {
            convertedNumber = inputNumber * 0.0003048;
            JOptionPane.showMessageDialog(null, convertedNumber + " kilometers");
        }
        else if (combo1 == "b" && combo2 == "d") {
            convertedNumber = inputNumber * 0.3048;
            JOptionPane.showMessageDialog(null, convertedNumber + " meters");
        }
        else if (combo1 == "c" && combo2 == "a") {
            convertedNumber = inputNumber * 0.621371;
            JOptionPane.showMessageDialog(null, convertedNumber + " miles");
        }
        else if (combo1 == "c" && combo2 == "b") {
            convertedNumber = inputNumber * 3280.84;
            JOptionPane.showMessageDialog(null, convertedNumber + " feet");
        }
        else if (combo1 == "c" && combo2 == "d") {
            convertedNumber = inputNumber * 1000;
            JOptionPane.showMessageDialog(null, convertedNumber + " meters");
        }
        else if (combo1 == "d" && combo2 == "a") {
            convertedNumber = inputNumber * 0.000621371;
            JOptionPane.showMessageDialog(null, convertedNumber + " miles");
        }
        else if (combo1 == "d" && combo2 == "b") {
            convertedNumber = inputNumber * 3.28084;
            JOptionPane.showMessageDialog(null, convertedNumber + " feet");
        }
        else if (combo1 == "d" && combo2 == "c") {
            convertedNumber = inputNumber * 0.001;
            JOptionPane.showMessageDialog(null, convertedNumber + " kilometers");
        }
        }
    }
}
private class CheckBoxListener implements ItemListener {
    public void itemStateChanged (ItemEvent e) {
        //Checks if the check box is checked
        if (myCheck.isSelected()){
            check = 'y';
        }
        else {
            check = 'n';
        }
    }
}
}

Answer 1

如果您的主要目标是使代码更整洁、更明确，那么我建议从以下开始:将单位数据类型从字符串转换为 Java enum 并封装Distance 类中的距离。这样做的好处是:

• 分离表示和转换逻辑
• 删除对 combo1 和 combo2 的临时困惑转换
• 删除长行的 if、else if 语句
• 允许在不更改表示逻辑的情况下添加新单元

以下是您可以使用的潜在结构的示例:

public enum Unit {
    MILES (1609.344),
    FEET (0.3048),
    KILOMETRES (1000.0),
    METRES (1.0);

    private final float toMetreRate;
    Unit(float toMetreRate) {
        this.toMetreRate = toMetreRate;
    }

    public float convertTo(float value, Unit unit) {
        return value * toMetreRate / unit.toMetreRate;
    }
}

public class Distance {
    private final Unit unit;
    private final float value;

    public Distance(float value, Unit unit) {
        this.value = value;
        this.unit = unit;
    }

    public Distance convert(Unit newUnit) {
        return new Distance(unit.covertTo(value, newUnit), newUnit);
    }
}