import java.io.*;
import java.util.*;
public class Add
{
public static void main(String args[])
{
try
{
float sum1=0,sum2=0,sum3=0,sum4=0,aver1=0,aver2=0,aver3=0,aver4=0;
int line = 0;
File f = new File("iris.txt");
InputStream input = new FileInputStream(f);
BufferedReader b = new BufferedReader(new InputStreamReader(input));
String value = b.readLine();
FileReader file=new FileReader("iris.txt");
BufferedReader in=new BufferedReader(file);
StringTokenizer fenxi;
while(value !=null)//读取文件的总行数
{
line++;
value = b.readLine();
}
b.close();
input.close();
String s[]=new String[line],str[][]=new String[line][4];
float a[][]=new float[line][4];
for(int i=0;i<150;i++)
{
s[i]=in.readLine();
fenxi=new StringTokenizer(s[i]);
while(fenxi.hasMoreTokens())
{
for(int j=0;j<4;j++)
{
str[i][j]=fenxi.nextToken();
a[i][j]=Float.parseFloat(str[i][j]);
}
}
System.out.println(s[i]);
}
for(int i=0;i<line;i++)
{
sum1=sum1+a[i][0];
aver1=sum1/150;
sum2=sum2+a[i][1];
aver2=sum2/150;
sum3=sum2+a[i][2];
aver3=sum3/150;
sum4=sum4+a[i][3];
aver4=sum4/150;
}
System.out.println("第一列的和："+sum1+"\n"+"平均值是："+aver1);
System.out.println("第二列的和："+sum1+"\n"+"平均值是："+aver2);
System.out.println("第三列的和："+sum1+"\n"+"平均值是："+aver3);
System.out.println("第四列的和："+sum1+"\n"+"平均值是："+aver4);
}
catch(IOException e)
{
System.out.println("找不到文件!");
}
}
}

错误处在这里，没看明白你的代码
for(int j=0;j<4;j++)
{
str[i][j]=fenxi.nextToken();
a[i][j]=Float.parseFloat(str[i][j]);
}