窗体程序计算一元二次方程

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问题描述：

设计一个一元二次方程类，包含三个属性（方程的3个系数），包含计算器求根的方法。

窗体中使用三个文本框和一个文本区，其中三个文本框用来输入方程的系数；文本区用来显示方程的根。

窗体中有一个按钮，用户点击该按钮后，程序获取三个系数构建仿佛方程对象，并调用方法计算方程的根在文本区中显示。

1.定义一元二次方程类SquareEquation

public class SquareEquation {double a,b,c;public void setA(double a){this.a=a;}public void setB(double b){this.b=b;}public void setC(double c){this.c=c;}public double getRootOne(){double disk=calculateValidDisk();return (-b+Math.sqrt(disk))/(2*a);}public double getRootTwo(){double disk=calculateValidDisk();return (-b-Math.sqrt(disk))/(2*a);}private double calculateValidDisk(){if(a==0){throw new EquationException("不是二次方程",EquationException.NONE_EQUATION);}double disk=b*b-4*a*c;if(disk<0){throw new EquationException("没有实根",EquationException.NO_REAL_ROOT);}return disk;}}class EquationException extends RuntimeException{public static final int NONE_EQUATION=1;public static final int NO_REAL_ROOT=2;private int errorCode;public EquationException(String msg,int errerCode){super(msg);this.errorCode=errorCode;}public int getErroeCode(){return errorCode;}}

2.定义窗体类EquationFrame,继承自JFrame

import java.awt.*;import java.awt.event.*;import javax.swing.*;public class EquationFrame extends JFrame implements ActionListener{SquareEquation equation;JTextField textA,textB,textC;JTextArea showRoots;JButton controlButton;public EquationFrame(){equation=new SquareEquation();textA=new JTextField(8);textB=new JTextField(8);textC=new JTextField(8);controlButton =new JButton("确定");JPanel pNorth=new JPanel();pNorth.add(new JLabel("二次项系数："));pNorth.add(textA);pNorth.add(new JLabel("一次项系数："));pNorth.add(textB);pNorth.add(new JLabel("常数项系数："));pNorth.add(textC);pNorth.add(controlButton);controlButton.addActionListener(this);getContentPane().add(pNorth,BorderLayout.NORTH);showRoots=new JTextArea();JScrollPane scrollPane=new JScrollPane(showRoots);getContentPane().add(scrollPane,BorderLayout.CENTER);setSize(630,160);Dimension scnSize=Toolkit.getDefaultToolkit().getDefaultToolkit().getScreenSize();Dimension frmSize=this.getSize();this.setLocation((scnSize.width-frmSize.width)/2,   (scnSize.height-frmSize.height)/2);validate();setVisible(true);this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);}public void actionPerformed(ActionEvent e){try{double a=Double.parseDouble(textA.getText());double b=Double.parseDouble(textB.getText());double c=Double.parseDouble(textC.getText());equation.setA(a);equation.setB(b);equation.setC(c);showRoots.append("根: "+equation.getRootOne());showRoots.append(" 根："+equation.getRootTwo()+"\n");}catch(Exception ex){showRoots.append(ex.getMessage()+"\n");}}}

3.测试类

public class Text {public static void main(String args[]){new EquationFrame();}}

4.运行结果

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