ReadCsv.java

amitsen01ei

Feb 17th, 2024

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import java.nio.file.*;
import java.time.*;
import java.util.*;
import java.util.function.Function;
import java.util.stream.Collectors;
import static common.io.Commons.println;
import static java.util.Map.Entry;
/**
* A csv file of size 1.85 GB containing 10000000 rows of uuids each row having 5 comma separated uuid
*/
final String inputPath = "/Users/amitsen01ei/Downloads/uuids-medium.csv";
void main() {
withStream();
}
void withStream() {
try (var inputStream = Files.lines(Path.of(inputPath))) {
var start = Instant.now();
inputStream
.map(this::rowReduce)
.flatMap(charMap -> charMap.entrySet().stream())
.collect(Collectors.toMap(Entry::getKey, Entry::getValue, Long::sum))
.entrySet()
.forEach(System.out::println);
println(STR."Time Taken : \{Duration.between(start, Instant.now()).getSeconds()} seconds");
} catch (Exception ex) {
System.err.println(ex.getMessage());
}
}
Map<Character, Long> rowReduce(String row) {
return Arrays.stream(row.split(","))
.flatMap(uuid -> uuid.chars().mapToObj(i -> (char) i))
.filter(ch -> ch != '-')
.collect(Collectors.toMap(Function.identity(), _ -> 1L, Long::sum));
}

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