example4_4.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 Example4_4 extends Applet
{   public double f(double x)
    {double y;
     y=x*(x*x*x*x+1)-1;
     return y;
	}

	public double lfs(double x,double eps)
    { double[] y=new double[10];
	  double[] a=new double[10];
	  int i=2,j;
	  a[0]=x;y[0]=f(x);y[1]=f(x+0.1);
	  a[1]=(y[1]-y[0])*10;
	  x=a[0]-y[0]/a[1];
	  while(i<10)
	  {a[i]=x;y[i]=f(x);
	   if(Math.abs(y[i])<eps)return x;
	   for(j=0;j<i;j++)a[i]=(y[i]-y[j])/(a[i]-a[j]);
	   x=a[i];
	   for(j=i-1;j>=0;j--)x=a[j]-y[j]/x;
	   i++;
	  }
	 return x;
	}

	public void paint(Graphics g)
	{double x=1,y,eps=1e-7;
	 y=f(x);
	 while(y>eps){x=lfs(x,eps);y=f(x);}
	 g.drawString("root="+x,10,20);
	 g.drawString("f(x)="+y,10,40);
	}
}