Java Application和Applet两种方式求一元二次方程ax2+bx+c=0的根

import java.awt.*; import java.applet.*; import java.text.DecimalFormat; /* <TITLE>Example</TITLE> <applet code="Experiment1" width=500 height=200> </applet> */ public class Experiment1 extends Applet{ DecimalFormat bd=new DecimalFormat("0.0000");//把double四舍五入取整 String str1,str2; public void init(){ setBackground(Color.red ); setForeground(Color.cyan); } void Solving(double a,double b,double c){ double x1,x2; double d=b*b-4*a*c; if(d>0){ x1=(-b+Math.sqrt(d))/(2*a); x2=(-b-Math.sqrt(d))/(2*a); str1=""+(int)a+"x2+"+(int)b+"x+"+(int)c+"=0 have two different real roots"; str2="x1="+bd.format(x1)+";x2="+bd.format(x2); } else if(d==0){ x1=-b/(2*a); str1=""+(int)a+"x2+"+(int)b+"x+"+(int)c+"=0 have one real root"; str2="x="+bd.format(x1); } else{ x1=-b/(2*a); x2=Math.sqrt(-d)/(2*a); str1=""+(int)a+"x2+"+(int)b+"x+"+(int)c+"=0 have two different Imaginary roots"; str2="x1="+bd.format(x1)+"+"+bd.format(x2)+"i;x2="+bd.format(x1)+"-"+bd.format(x2)+"i"; } } public void paint(Graphics g){ Solving(1,5,3); g.drawString(str1,20,20); g.drawString(str2,20,40); Solving(4,4,1); g.drawString(str1, 20,70); g.drawString(str2, 20,90); Solving(2,3,2); g.drawString(str1, 20,120); g.drawString(str2, 20,140); showStatus("This is a example of solving x"); } }