example6_10.java

清华大学2002年出版的《科学与工程数值计算算法Java》配套源码

import java.applet.*;
import java.awt.*;

public class Example6_10 extends Applet
{
 public static double f(double x)
 {double y;
  y=x*Math.cos(x);
  return y; }

 public static double Filon(double a,double b,int n,int N)
  {double x,s1,s2,alpha,beta,gama,sita,h,c,s,t,y;
   h=(b-a)/2/N;sita=n*h;c=Math.cos(sita);s=Math.sin(sita);t=Math.pow(sita,3);
   alpha=(sita*(sita+s*c)-2*s*s)/t;
   beta=2*(sita*(1+c*c)-2*s*c)/t;
   gama=4*(s-sita*c)/t;
   s1=(f(a)*Math.sin(n*a)+f(b)*Math.sin(n*b))/2;
   x=a+2*h;
   while(x<b){s1+=f(x)*Math.sin(n*x);x+=2*h;}
   x=a+h;s2=0;
   while(x<b){s2+=f(x)*Math.sin(n*x);x+=2*h;}
   y=alpha*(f(a)*Math.sin(n*a)-f(b)*Math.cos(n*b))+beta*s1+gama*s2;
   y*=h;
   return y;
}
public void paint(Graphics g)
{double y,y1,y2,y3;int n;
 g.drawString("׼ȷֵ                                       F7                                       F9                                       F11",10,20);
 for(n=10;n<=30;n+=10)
 {  y=-2*n*Math.PI/(n*n-1);
    y1=Filon(0,2*Math.PI,n,7*n/2);
    y2=Filon(0,2*Math.PI,n,9*n/2);
    y3=Filon(0,2*Math.PI,n,11*n/2);
  g.drawString(""+y+"  "+y1+"  "+y2+"  "+y3,10,20+n*2);}
}
}