Taking out elements from a matrix thus reducing its dimension

[theodorekon]

Hi,
I have written a program in Java2 which reads a txt file and stores each line of the file in a matrix called lines[]. Now what I want to do is to read through this matrix and take out some of its elements thus reducing its dimension. For example some of the lines in my file start with // which means that they are comments and I want to exclude those from my matrix. Some other lines are blank and I also want to exclude them. To make it more clear I give the example below:

I have the input.txt file which is as follows

// This is a comment
234
44
// This is also a comment
werg
bf

34r2
dfv
// End of file

My code is:

                int numLines=0;
		scanLines = new Scanner(new BufferedReader(new FileReader("input.txt")));
		scanLines.useDelimiter("\n");

        	while (scanLines.hasNext()) {
				lines[numLines]=scanLines.next().trim();
				numLines++;
        	}

Now the matrix created is:
lines[// This is a comment, 234, 44, // This is also a comment, werg, bf, , 34r2, dfv, // End of file]
which has a dimension of 10. I want to exlude the lines which start with // and the ones that are blank and end up with the matrix:
lines[234, 44, werg, bf, 34r2, dfv,]
which has a dimension of 6.

Any ideas??

[StormyWaters]

Why are you using an array? Is this a necessity?

If not I would suggest switching over to a List interface, ArrayList should be fine. This type of an interface makes dealing with the removal or addition of data much simplier.

If you must stick with arrays, you will probably need to iterate through the array twice. Once to get the total number of lines to put in the new array. And the second time to actually put the lines in the new array.

[j2me64]

Any ideas??

hi, with a simple if-statement you could exclude the unwanted lines in the while-loop. or use the class arraylist to store your lines and then use the method remove() the unwanted elements.

[theodorekon]

hi, with a simple if-statement you could exclude the unwanted lines in the while-loop. or use the class arraylist to store your lines and then use the method remove() the unwanted elements.

The problem is that when I use in the while loop the statement

if(scanLines.next!="") {...}

it jumps a line every time it runs the while loop. As a result the lines[] matrix only gets half of the lines of the txt file. Do you have any other if statement I could use??

[j2me64]

The problem is that when I use in the while loop the statement

if(scanLines.next!="") {...}

it jumps a line every time it runs the while loop. As a result the lines[] matrix only gets half of the lines of the txt file. Do you have any other if statement I could use??

Declare the String s and then use

while ((s=scanLines.hasNext())) {
if (!s.contains("\\"))

for saying: if the string s does not contain "\\" then continue.

[theodorekon]

Declare the String s and then use

while ((s=scanLines.hasNext())) {
if (!s.contains("\\"))

for saying: if the string s does not contain "\\" then continue.

It doesn't work. It says:

ScanXan5.java:43: incompatible types
found : boolean
required: java.lang.String
while ((s=scanLines.hasNext())) {
^
ScanXan5.java:43: incompatible types
found : java.lang.String
required: boolean
while ((s=scanLines.hasNext())) {
^
2 errors