Problem in File Handling in Java

[getbiplab]

We have 3 files file1, file2, file3......Say, File1 contains 10 lines (absolute path names of 10 different files ) and file2 has 4 lines .......all the lines of file2 are there in file1 also.......What we want is to copy the content of file1 in file3 without those lines which are there in file2....Can anybody please give the java code for this....

file1

/x/guest/english/1.txt
/x/guest/english/2.txt
/x/guest/english/3.txt
/x/guest/english/4.txt
/x/guest/english/5.txt
/x/guest/english/6.txt
/x/guest/english/7.txt
/x/guest/english/8.txt
/x/guest/english/9.txt
/x/guest/english/10.txt

file2

/x/guest/english/10.txt
/x/guest/english/6.txt
/x/guest/english/3.txt
/x/guest/english/8.txt

file3

/x/guest/english/1.txt
/x/guest/english/2.txt
/x/guest/english/4.txt
/x/guest/english/5.txt
/x/guest/english/7.txt
/x/guest/english/9.txt

[Eranga]

First read all files line-by-line and store the read values in separate arrays. Then by simply comparing write values to any file you want.

[DonCash]

Heres a quick example to get you started.

This code reads a file in line by line and adds each value to an array.

Code:

FileInputStream in = new FileInputStream("file1.txt");
BufferedReader br = new BufferedReader(new InputStreamReader(in));

String strLine;
String[] myarray;
myarray = new String[10];
		
while ((strLine = br.readLine()) != null) {
			
for (int j = 0; j < myarray.length; j++){
myarray[j] = br.readLine();
}
				
}
in.close();

Code:

System.out.println(myarray[0]);
System.out.println(myarray[1]);
System.out.println(myarray[2]);

etc..

[Eranga]

Yes it's nice work. Do the same thing for you next file and when you write to the file compare elements and write.

[Eranga]

No pal, how bad me. My dear Don, check your read line. You store in a string in the array by skipping first line. So you should have null pointer exception in this code. Isn't it?

How about something like this.

Code:

            while((firstFile[i] = br.readLine()) != null){
                System.out.println(firstFile[i]);
            }

[DonCash]

Ah yeah Eranga, your right.

This does actually skip the first line. I didn't test this first as I did it from memory.

You get the idea though... lol

[Eranga]

Quote:

Originally Posted by DonCash

Ah yeah Eranga, your right.

This does actually skip the first line. I didn't test this first as I did it from memory.

You get the idea though... lol

Me too pal, not tested at all. Seen it in last minute actually.