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package pgdp.streams;
 
import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.time.LocalDate;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.function.Function;
import java.util.stream.Collectors;
import java.util.stream.Stream;
 
public abstract class Temperatures {
    protected List<Temperature> data;
 
    public Temperatures(String filepath) {
        data = parseCsvFile(new File(filepath));
    }
 
    public Stream<Temperature> stream() {
        return data.stream();
    }
 
    static private List<Temperature> parseCsvFile(final File csvFile) {
        try {
            return Files.lines(csvFile.toPath()).skip(1) // skip header of csv file
                    .map(lineToTemperature) // convert line to DateTemperature
                    .filter(elem -> elem != null) // filter null values due to parsing errors
                    .collect(Collectors.toList());
        } catch (IOException e) {
            throw new RuntimeException("File " + csvFile + " not found.");
        }
    }
 
    static private Function<String, Temperature> lineToTemperature = (line) -> {
        try {
            final String[] fields = line.split(","); // a CSV with comma-separated lines
            final LocalDate date = LocalDate.parse(fields[0]);
            final double avgTemperature = Double.parseDouble(fields[1]);
            // Skipping uncertainty
            final String city = fields[3];
            final String country = fields[4];
            final double latitude = Double.parseDouble(fields[5].substring(0, fields[5].length() - 1));
            final double longitude = Double.parseDouble(fields[6].substring(0, fields[6].length() - 1));
            return new Temperature(date, avgTemperature, city, country, latitude, longitude);
        } catch (Exception e) {
            return null;
        }
    };
 
 
}

Main.java:15: error: class Temperatures is public, should be declared in a file named Temperatures.java
public abstract class Temperatures {
                ^
Main.java:16: error: cannot find symbol
    protected List<Temperature> data;
                   ^
  symbol:   class Temperature
  location: class Temperatures
Main.java:22: error: cannot find symbol
    public Stream<Temperature> stream() {
                  ^
  symbol:   class Temperature
  location: class Temperatures
Main.java:26: error: cannot find symbol
    static private List<Temperature> parseCsvFile(final File csvFile) {
                        ^
  symbol:   class Temperature
  location: class Temperatures
Main.java:37: error: cannot find symbol
    static private Function<String, Temperature> lineToTemperature = (line) -> {
                                    ^
  symbol:   class Temperature
  location: class Temperatures
Main.java:47: error: cannot find symbol
            return new Temperature(date, avgTemperature, city, country, latitude, longitude);
                       ^
  symbol:   class Temperature
  location: class Temperatures
6 errors

Standard output is empty