example2_7.java

Java学习丛书科学与工程数值算法（Java版）一书的代码

import java.applet.*;
import java.awt.*;
public class Example2_7 extends Applet
{
  public static int  MRank(double[][] a,int n,int m)
  {int i,j,row,col,k;
   double max,temp;
   for(k=0;k<n;k++)
   {//找主元
    max=0;row=col=k;
    for(i=k;i<n;i++)
     for(j=k;j<m;j++)
     {temp=Math.abs(a[i][j]);
      if(max<temp){max=temp;row=i;col=j;}
	  }
	//交换行列，将主元调整到k行k列上
	if(max==0)return k;
	if(row!=k)
	{for(j=0;j<m;j++)
	 {temp=a[row][j];a[row][j]=a[k][j];a[k][j]=temp;}
	 }
	 if(col!=k)
	 {for(i=0;i<n;i++)
	   {temp=a[i][col];a[i][col]=a[i][k];a[i][k]=temp;}
	 }

	 for(j=k+1;j<m;j++)a[k][j]/=a[k][k];
	 for(j=k+1;j<m;j++)
	  for(i=k+1;i<n;i++)a[i][j]-=a[i][k]*a[k][j];
	 for(i=0;i<k;i++)a[i][k]=0;
	 a[k][k]=1;
  }
  return n;
 }

public void paint(Graphics g)
{double[][] a={{0.23,0.24,0.25,1.26},{1.11,0.12,0.13,0.14},{0.15,1.16,0.17,0.18}};
 double[][] b={{1,2,3,4},{5,-5,1,8},{11,8,5,-7},{5,-1,-3,-1},{7,5,6,8}};
 int rank;
 rank=MRank(a,3,4);
 g.drawString("Rank(A)="+rank,10,20);
 rank=MRank(b,5,4);
 g.drawString("Rank(B)="+rank,10,40);
 }
}