[java]代码库import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class Chp13_1 extends JFrame{

private JButton jisuan;

private JPanel panel1,panel2,panel3,panel4;

private JTextField field1,field2,field3;

private JLabel label1,label2,label3,label4;

private JTextArea area;

private Container container;

Chp13_1(){

super("计算一元二次方程的根");

container = getContentPane();

container.setLayout(new FlowLayout());

label4 = new JLabel("请依次输入一元二次方程的三个系数，并点击计算显示实根");

container.add(label4);

panel1 = new JPanel();

label1 = new JLabel("系数a");

field1 = new JTextField(10);

panel1.add(label1);

panel1.add(field1);

panel2 = new JPanel();

label2 = new JLabel("系数b");

field2 = new JTextField(10);

panel2.add(label2);

panel2.add(field2);

panel3 = new JPanel();

label3 = new JLabel("系数c");

field3 = new JTextField(10);

panel3.add(label3);

panel3.add(field3);

panel4 = new JPanel();

panel4.setLayout(new GridLayout(1,3,1,2));

panel4.add(panel1);

panel4.add(panel2);

panel4.add(panel3);

container.add(panel4);

jisuan = new JButton("计算");

jisuan.addActionListener(

new ActionListener(){

public void actionPerformed(ActionEvent event) {

double a = Double.parseDouble(field1.getText());

double b = Double.parseDouble(field2.getText());

double c = Double.parseDouble(field3.getText());

double deerta = b*b-4*a*c;

if(deerta < 0){

area.setText("无实根");

}else {

double x1 = (Math.sqrt(deerta)-b)/(2*a);

double x2 = (-Math.sqrt(deerta)-b)/(2*a);

area.setText("实根1 = "+x1+"\n实根2 = "+x2);

}

}

}

);

container.add(jisuan);

area = new JTextArea(10,15);

area.setText("该方程的实根为");

container.add(area);

setSize(500,400);

setVisible(true);

}

public static void main(String[] args) {

Chp13_1 application = new Chp13_1();

application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}

}