roots1.java

使用Java 编写求一元方程的根,并且是使用小程序完成的

import javax.swing.*;
import java.awt.*;
import java.applet.*;
public class roots1 extends Applet
{
   public void paint(Graphics g)
   	{
   		double a,b,c,deta;
   		double x1,x2;
   		a=Double.parseDouble(JOptionPane.showInputDialog("Enter an amout in double,for example 11.25"));
   		b=Double.parseDouble(JOptionPane.showInputDialog("Enter an amout in double,for example 11.2"));
   		c=Double.parseDouble(JOptionPane.showInputDialog("Enter an amout in double,for example 1.25"));
   		deta=b*b-4*a*c;
   		if(deta==0)
   			{
   				x1=(-b)/(2*a);
   				x2=x1;
   				g.drawString("x1="+x1,20,40);
   				g.drawString("x2="+x1,20,60);
   			}
   			else if(deta>0)
   				{
   					x1=(-b+(float)Math.sqrt(deta))/(2*a);
					x2=(-b-(float)Math.sqrt(deta))/(2*a);
					g.drawString("x1="+x1,20,40);
					g.drawString("x2="+x2,20,60);
				}
				else if(deta<0)
					g.drawString("equation no real root",20,40);     
       }
 }