comparing two output lines.

[shana07]

I need help on comparing lines in my output file...
How to delete the second line in text file (FileReader) and print out the first line for the same fileno?

I put here sample of my output file:

1 : 30 at 2
1 : 134 at 10
2 : 35 at 2
4 : 30 at 2
4 : 80 at 8
..........
...........

The problem here is, not all file numbers ([0]) have same file numbers.
What I can think is something like this..but I still got the repeated fileno in my new output file.

lineFRST = in1.readLine(); 
lineSEC = in1.readLine();      
 
while((lineFRST != null) && (lineSEC != null))   {    
...
String[] thelineFRST = lineFRST.split(" ");
String fileNo1 = thelineFRST[0];
 
String[] thelineSEC = lineSEC.split(" ");
String fileNo2 = thelineSEC[0];
 
if(fileNo1.equals(fileNo2)) {
               printWriter.println(lineFRST); 
            }
            else     {  
                printWriter.println(lineFRST); 
                printWriter.println(lineSEC); 
            } 
 

My new output should look like this:
1 : 30 at 2
2 : 35 at 2
4 : 30 at 2


Kindly please teach me...Thank you ....