Java学习笔记(4) 项目搭建实例

一个小的图形界面程序，进行摄氏度和华氏度的转换。还有输入空的异常抛出问题未解决，过后再修改。

1.Temp.java – –算法部分：温度类的创建，转换公式

[code]interface Temp{ 
    void calcTemp();
    double output();
}

class CTemp implements Temp{
    private double cTemp, fTemp;
    public CTemp(double c){
        cTemp = c;
    }
    public void calcTemp(){
        fTemp = cTemp*1.8+32;
    }
    public double output(){
        return fTemp;
    }
}

class FTemp implements Temp{
    private double cTemp, fTemp;
    public FTemp(double f){
        fTemp = f;
    }
    public void calcTemp(){
        cTemp = (fTemp-32)/1.8;
    }
    public double output(){
        return cTemp;
    }
}

2.MyException.java – – 自定义的异常类，从抽象的异常类中继承

[code]public class MyException extends Exception{
    private String message;
    //存
    public MyException(String m){
        message=m;
    }
    //取
    public String outMessage(){
        return message;
    }
}

3.MyFrame.java – – 图形界面

[code]import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;

public class MyFrame extends JFrame implements ActionListener{

    //面板
    JPanel pnlMain=new JPanel();

    //标签
    JLabel lblInputc=new JLabel("请输入摄氏温度：");
    JLabel lblInputf=new JLabel("请输入华氏温度：");
    JLabel lblOutputc=new JLabel("转换为摄氏温度：");
    JLabel lblOutputf=new JLabel("转换为华氏温度：");
    JLabel lblError=new JLabel("错误信息：");

    //文本框(参数：列宽)
    JTextField txtInputc=new JTextField(10);
    JTextField txtInputf=new JTextField(10);
    JTextField txtResultc=new JTextField(10);
    JTextField txtResultf=new JTextField(10);
    JTextField txtError=new JTextField(10); 

    //按钮
    JButton btnCalc=new JButton("计算");
    JButton btnCancle=new JButton("取消");    

    //新建MyException的对象，传入参数
    MyException mex=new MyException("输入温度越界");

    //构造函数
    public MyFrame(){
        //设置面板布局(网格布局:6行2列，行、列间距)
        pnlMain.setLayout(new GridLayout(6,2,5,5));
        pnlMain.add(lblInputc);
        pnlMain.add(lblInputf);
        pnlMain.add(txtInputc);
        pnlMain.add(txtInputf);
        pnlMain.add(lblOutputf);
        pnlMain.add(lblOutputc);
        pnlMain.add(txtResultf);
        pnlMain.add(txtResultc);
        pnlMain.add(lblError);
        pnlMain.add(txtError);
        pnlMain.add(btnCalc);
        pnlMain.add(btnCancle);

        //在按钮上加监听器,检测自己是否被点击
        btnCalc.addActionListener(this);
        btnCancle.addActionListener(this);

        //把面板放到界面上
        setContentPane(pnlMain);
    }   

    //获取文本输入
    //异常方法：抛出自己
    public String inputTextc() throws MyException{
        String str=new String();
        str=txtInputc.getText();
        if(Double.parseDouble(str)<-273.15){
            throw mex;
        }
        return str;
    }
    public String inputTextf() throws MyException{
        String str=new String();
        str=txtInputf.getText();
        if(Double.parseDouble(str)<-459.67){
            throw mex;
        }
        return str;
    }

    //构造函数之后加入事件方法，包括抽象方法(ActionListener监听器中)的实现
    //抛出异常：数字格式异常 throws NumberFormatException
    public void actionPerformed(ActionEvent ae){
        //调用inputText
        try{
            if(ae.getSource()==btnCalc){
                //捕获文本框内容并转换为double类型
                CTemp cobj=new CTemp(Double.parseDouble(inputTextc()));
                cobj.calcTemp();
                    //将计算结果转换为字符串并输出,""+ :强制转换
                txtResultf.setText(""+cobj.output());
                FTemp fobj=new FTemp(Double.parseDouble(inputTextf()));
                fobj.calcTemp();
                txtResultc.setText(""+fobj.output());
                txtError.setText("");
            }else if(ae.getSource()==btnCancle){
                //取消：清空文本框
                txtInputc.setText("");
                txtInputf.setText("");
                txtResultc.setText("");
                txtResultf.setText("");
                txtError.setText("");
            }
        }catch(MyException me){
            txtError.setText("异常："+ me.outMessage());
        }catch(NumberFormatException nfe){
            txtError.setText("数字格式异常："+ nfe.getMessage());
        }catch(Exception e){
            txtError.setText("异常："+ e.getMessage());
        }
    }
}

4.MainProg.java – – 主程序

[code]import java.lang.*;
import java.io.*;
import java.util.*;
import javax.swing.*;

public class MainProg{

    public static void main(String[] args) throws IOException{
        MyFrame mf=new MyFrame();
        //标题
        mf.setTitle("温度转换");
        //大小
        mf.setSize(400,200);
        //关闭
        mf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        //可见：显示界面
        mf.setVisible(true);
    }
}