example6_7.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.awt.*;
import java.applet.*;
public class Example6_7 extends Applet
{
 public static double f(double x)
 {double y;
  y=Math.sin(x)+Math.pow(x,5);
  return y; }

 public static double GaussLaguerre(int n)
  {double s;
   double[] y=new double[5];
   double[] x=new double[5];
   int i;
   if(n==1){x[0]=1;y[0]=1;}
   else if(n==2){x[0]=0.5857864;x[1]=3.4142136;y[0]=0.8535534;y[1]=0.1464466;}
   else if(n==3){x[0]=0.4157746;x[1]=2.2942804;x[2]=6.2899451;
                 y[0]=0.7110930;y[1]=0.2785177;y[2]=0.0103893;}
   else if(n==4){x[0]=0.3225477;x[1]=1.7457611;x[2]=4.5366203;x[3]=9.3950709;
                 y[0]=0.6031541;y[1]=0.3574187;y[2]=0.0388879;y[3]=0.0005393;}
   else if(n==5){x[0]=0.2635603;x[1]=1.4134031;x[2]=3.5964258;x[3]=7.0858100;x[4]=12.6408008;
                 y[0]=0.5217556;y[1]=0.3986668;y[2]=0.0759424;y[3]=0.0036118;y[4]=0.0000234;}
   s=0;
   for(i=0;i<n;i++){s+=y[i]*f(x[i]);}
   return s;

}
public void paint(Graphics g)
{double y;
 int n;
 for(n=1;n<=5;n++)
 {y=GaussLaguerre(n);
  g.drawString("I"+n+"="+y,10,20*n);
 }
}}