我有一个CSV文件，其中包含大约500,000行和22列的航班数据。第5列包含每次飞行的每个飞机的机尾号。第22列包含每次飞行的行进距离。我试图将每个尾号（第5列）的总行驶距离（第22列）相加。
我创建了一个HashMap，其中包含所有名为map1的数据。我创建了一个名为HashMap的第二个planeMileages来放置每个航班号及其进去的总距离。我正在使用嵌套的if语句遍历map1的每一行，并查看planeMileages中是否已包含尾号。如果它在planeMileages中，那么我想将该键添加到accumulatedMileages上。如果不包含它，我想输入密钥以及它的第一个距离值。
我写的当前代码对我来说听起来不错，但是它产生了错误的结果，输出了不正确的尾号。您能否看一下并让我知道主要方法中忽略的内容？谢谢！
public class FlightData {
HashMap<String,String[]> dataMap;
public static void main(String[] args) {
FlightData map1 = new FlightData();
map1.dataMap = map1.createHashMap();
HashMap<String, Integer> planeMileages = new HashMap();
//Filling the Array with all tail numbers
for (String[] value : map1.dataMap.values()) {
if(planeMileages.containsKey(value[4])) {
int accumulatedMileage = planeMileages.get(value[4]) + Integer.parseInt(value[21]);
planeMileages.remove(value[4]);
planeMileages.put(value[4], accumulatedMileage);
}
else {
planeMileages.put(value[4],Integer.parseInt(value[21]));
}
}
String maxKey = Collections.max(planeMileages.entrySet(), Map.Entry.comparingByValue()).getKey();
System.out.println(maxKey);
}
public HashMap<String,String[]> createHashMap() {
File flightFile = new File("flights.csv");
HashMap<String,String[]> flightsMap = new HashMap<String,String[]>();
try {
Scanner s = new Scanner(flightFile);
while (s.hasNextLine()) {
String info = s.nextLine();
String [] piecesOfInfo = info.split(",");
String flightKey = piecesOfInfo[4] + "_" + piecesOfInfo[2] + "_" + piecesOfInfo[11]; //Setting the Key
String[] values = Arrays.copyOfRange(piecesOfInfo, 0, piecesOfInfo.length);
flightsMap.put(flightKey, values);
}
s.close();
}
catch (FileNotFoundException e)
{
System.out.println("Cannot open: " + flightFile);
}
return flightsMap;
}
}
请在下面查看我的CSV文件的几行：
DayofMonth DayOfWeek FlightDate UniqueCarrier TailNum OriginAirportID Origin OriginStateName DestAirportID Dest DestStateName DepTime DepDelay WheelsOff WheelsOn ArrTime ArrDelay Cancelled CancellationCode Diverted AirTime Distance
3 1 10/3/2016 AA N786AA 10721 BOS Massachusetts 12478 JFK New York 556 -4 623 703 709 -6 0 0 40 187
4 2 10/4/2016 AA N794AA 10721 BOS Massachusetts 12478 JFK New York 554 -6 615 703 712 -3 0 0 48 187
1 6 10/1/2016 AA N783AA 12478 JFK New York 12892 LAX California 823 -7 844 1104 1111 -30 0 0 320 2475
2 7 10/2/2016 AA N798AA 12478 JFK New York 12892 LAX California 847 17 904 1131 1159 18 0 0 327 2475
3 1 10/3/2016 AA N786AA 12478 JFK New York 12892 LAX California 825 -5 838 1109 1131 -10 0 0 331 2475
4 2 10/4/2016 AA N794AA 12478 JFK New York 12892 LAX California 826 -4 848 1114 1132 -9 0 0 326 2475
最佳答案
您好，您可以检查一下吗？
public static void main(String[] args) throws IOException {
Map<String, String[]> map = createMap();
Map<String, Long> planeMileages = map
.entrySet()
.stream()
.collect(Collectors.groupingBy(o -> o.getValue()[4],
Collectors.collectingAndThen(
Collectors.summarizingInt(value ->
Integer.parseInt(value.getValue()[21])), IntSummaryStatistics::getSum
)
));
String maxKey = planeMileages.entrySet().stream().max(Comparator.comparing(Map.Entry::getValue)).get().getKey();
System.out.println("max key: "+ maxKey);
}
public static Map<String, String[]> createMap() throws IOException {
try (BufferedReader a = Files.newBufferedReader(Paths.get("flights.csv"))) {
return a.lines().map(s -> s.split(","))
.collect(Collectors.toMap(piecesOfInfo -> String.join("_", piecesOfInfo[4], piecesOfInfo[2], piecesOfInfo[11]), Function.identity()));
}
}
public static Map<String, String[]> createMapLastDupWins() throws IOException {
try (BufferedReader a = Files.newBufferedReader(Paths.get("flights.csv"))) {
return a.lines().map(s -> s.split(","))
.collect(Collectors.toMap(piecesOfInfo -> String.join("_", piecesOfInfo[4], piecesOfInfo[2], piecesOfInfo[11]), Function.identity(), (strings, strings2) -> {
//if this helps than data is duplicated
return strings2;
}));
}
}