example3_6.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 Example3_6 extends Applet
{
  public static boolean  zhuigan(double[] a,double[] b,double c[],double d[], int n)
  { int i;
    for(i=1;i<n;i++)
    { if (b[i-1]==0)return false;
      a[i]/=b[i-1];
      b[i]-=a[i]*c[i-1];
      d[i]-=a[i]*d[i-1];
    }

    d[n-1]/=b[n-1];
    for(i=n-2;i>=0;i--)d[i]=(d[i]-c[i]*d[i+1])/b[i];
	return true;
   }

  public void paint(Graphics g)
   {double[] a ={0,1,1};
    double[] b ={-2,-2,-2};
    double[] c ={1,1,0};
    double[] d ={-2,1,-4};
    int i,n=d.length;
    if(zhuigan(a,b,c,d,3))
    { for(i=0;i<n;i++)
      g.drawString("X"+i+"="+d[i]+" ",10,i*20+20);
    }
    else
    g.drawString("追赶法失效!",10,20);
    }

}