example5_5.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 Example5_5 extends Applet
{
 public double enpqs(double[] x,double[] y,double t)
 {int i,j,k,l,n=x.length;
  double[] b=new double[n];
  double f;
  b[0]=y[0];
  for(i=1;i<n;i++)
  {b[i]=y[i];
   for(j=0;j<i;j++)b[i]=(x[i]-x[j])/(b[i]-b[j]);
  }
  f=b[n-1];
  for(i=n-2;i>=0;i--)f=b[i]+(t-x[i])/f;
  return f;
 }

 public void paint(Graphics g)
 {double[] x={-1,-0.80,-0.65,-0.40,-0.30,0,0.20,0.45,0.80,1};
  double[] y=new double[10];
  double f,h;
  int i;
  for(i=0;i<10;i++)y[i]=1.0/(1+25*x[i]*x[i]);
  f=enpqs(x,y,-0.85);h=1.0/(1+25*0.85*0.85);
  g.drawString("t=-0.85  f(t)="+f+"  实际值="+h,10,20);
  f=enpqs(x,y,0.25);h=1.0/(1+25*0.25*0.25);
  g.drawString("t=0.25   f(t)="+f+"  实际值="+h,10,40);
  }
}