有办法从ArrayList中挑选特定的元素吗？

Question

39.95 41.1667 2002 04 -9999 -9999 420

ArrayList<TempRead> t = new ArrayList();

public class TempRead {
private double latitude = -100;
private double longitude = -180;
private int year = 0;
private int month = 0;
private double maxTemp = -9999;
private double minTemp = -9999;
private double avgTemp = -9999;

public TempRead(){}

public TempRead(double latitude, double longitude, int year, int month, double maxTemp, double minTemp, double avgTemp){
    this.latitude = latitude;
    this.longitude = longitude;
    this.month = month;
    this.year = year;
    this.maxTemp = maxTemp;
    this.minTemp = minTemp;
    this.avgTemp = avgTemp;
}

public double getLatitude(){
    return latitude;
}

public double getLongitude(){
    return longitude;
}

public int getMonth(){
    return month;

}

public int getYear(){
    return year;
}

public double getMaxTemp(){
    return maxTemp;
}

public double getMinTemp(){
    return minTemp;
}

public double avgTemp(){
    return avgTemp;
}

@Override
public String toString(){
    return latitude + " " + longitude + " " + year + " " + month + " " + maxTemp + " " + minTemp + " " + avgTemp + " ";
}

System.out.println(t.get(0));

编辑：以下是我的主要内容：

public static void main(String[] args) {
    ArrayList<TempRead> t = new ArrayList();
    readFile(t);
    avgAllTemps(t);
}

public static void readFile(ArrayList<TempRead>t){
        try{
        String userFileName;
        Scanner in = new Scanner(System.in);
        System.out.println("Enter name of file: ");
        userFileName = in.next();
        System.out.println();

        Scanner file = new Scanner(new File(userFileName));

        while(file.hasNext()){
            t.add(new TempRead(file.nextDouble(), file.nextDouble(), file.nextInt(), file.nextInt(), file.nextDouble(), file.nextDouble(), file.nextDouble()));
        }
    }catch(IOException e){
        System.out.println(e);
    }
}

public static void avgTemps(ArrayList<TempRead>t){
    double totalMinTemp = 0.0;
    int count = 0;
    for (TempRead entry : t) {
        if (entry.getMinTemp() != -9999) {
            totalMinTemp += entry.getMinTemp();
            count++;
        }
        double avgMinTemp = totalMinTemp / count;
        System.out.println("Avg of min temps in arraylist: " + avgMinTemp);
    }
}

Answer 1

在查找温度时，不应查找ArrayList的最后3个元素，而应查找ArrayList中每个元素内部的数据

从第一个入口获得温度：

TempRead entry = t.get(0);
double maxTemp = entry.getMaxTemp();
double minTemp = entry.getMinTemp();
double avgTemp = entry.avgTemp();
//do stuff

如果需要每个条目，请使用循环：

for(TempRead entry : t)
{
    double maxTemp = entry.getMaxTemp();
    double minTemp = entry.getMinTemp();
    double avgTemp = entry.avgTemp();
    //do stuff
}

double totalMinTemp = 0.0;
int count = 0;
for(TempRead entry : t)
    if(entry.getMinTemp() != -9999)
    {
        avgMinTemp += entry.getMinTemp();
        count++;
    }
double avgMinTemp = totalMinTemp / count;

double avgMinTemp = t.stream().filter(t -> t.getMinTemp() != -9999).collect(Collectors.averaging(TempRead::getMaxTemp‌​));