0

```
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import java.io.*;
import java.text.*;
import java.util.regex.*;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
class Clustering1
{
public static void main(String[] args) throws IOException, FileNotFoundException
{
int diff_matrix[][] = new int[500][500];
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter the data file name\n");
String fname=br.readLine();
File file = new File(fname);
if (file.exists())
{
FileReader fr = new FileReader(file);
LineNumberReader ln = new LineNumberReader(fr);
int n = 0;
while (ln.readLine() != null)
n++;
ln.setLineNumber(1);
for(int i=1;i<n-1;i++)
{
for(int j=1;j<n-1;j++)
{
if(i!=j)
{
ln.setLineNumber(i);
String line1=ln.readLine();
Pattern pat = Pattern.compile("[ ,]");
ln.setLineNumber(j);
String line2=ln.readLine();
String str1[]=pat.split(line1);
String str2[]=pat.split(line2);
int count=0;
int s=0;
for(int p=0; p < str1.length; p++)
{
if(str1[p].equals(str2[p]))
count=count+1;
}
diff_matrix[i-1][j-1]=count;
}
else
diff_matrix[i-1][j-1]=0;
}
}
for(int i=0;i<n-2;i++)
{
System.out.println();
for(int j=0;j<n-2;j++)
{
System.out.print(diff_matrix[i][j]+"\t");
}
}
int neigh_matrix[][] = new int[500][500];
int nm=0;
int k=1;
int min_matrix[]=new int[500];
for(int i=0;i<n-1;i++)
{
int min=diff_matrix[i][k];
for(int j=0;j<n-1;j++)
{
if(i!=j){
if(min>diff_matrix[i][j])
{
min=diff_matrix[i][j];
}
}
}
min_matrix[i]=min;
k=0;
}
for(int i=0;i<n-1;i++)
{
neigh_matrix[i][nm]=i+1;
for(int j=0;j<n-1;j++)
{
if(min_matrix[i]==diff_matrix[i][j])
{
neigh_matrix[i][++nm]=j+1;
}
}
}
for(int i=0;i<n-1;i++)
{
System.out.println();
for(int j=0;j<neigh_matrix[i].length;j++)
System.out.println(neigh_matrix[i][j]+"\t");
}
int clusters[][] = new int[500][500];
}
else
{
System.out.println("File is not exist");
}
}
}
```

i am not getting correct output.. can u solve it

```
my error is:Exception in thread "main" java.lang.NullPointerException
at java.util.regex.Matcher.getTextLength(Matcher.java:1127)
at java.util.regex.Matcher.reset(Matcher.java:284)
at java.util.regex.Matcher.<init>(Matcher.java:205)
at java.util.regex.Pattern.matcher(Pattern.java:879)
at java.util.regex.Pattern.split(Pattern.java:988)
at java.util.regex.Pattern.split(Pattern.java:1050)
at Clustering.main(Clustering.java:39)
```