For example my input csv file contains:
A B C D E
10 ab a1 b1 ab1
20 cd c1 d1 cd1
30 ef e1 f1 ef1
40 gh c1 h1 gh1
My output:
A
10
20
30
40
I am able to do it by traversing each row. But I don't want like that. I have hundreds of thousands of records in my csv so I want all column values of A at a time. I want to use only apache common csv.
There is no way to read only the first column of a CSV file without reading whole lines in one way or another. This is a text file without fixed record sizes.
For a binary file with a fixed size of bytes for each record this would be possible e.g. with a RandomAccessFile. But with a text file you have always to search for the end of line to find the beginning of the next row and the next field in column A.
But I don't think this is a big problem when you read line by line and don't hold the unwanted column values in memory.
Usually, we get CSVRecord when we read the .csv files. You can use below code to get first column. But Apache CSV will internally Parse all the columns and return it as CSVRecord.
Reader in = new FileReader("input1.csv");
Iterable<CSVRecord> records = CSVFormat.EXCEL.parse(in);
for (CSVRecord record : records) {
System.out.println(record.get(0));
}
