How to find the max element from an array list of objects?

Question

Collections.max(arraylist) doesn\'t work, and a regular for loop won\'t work either.

What I have is:

ArrayList

        

Answer 1

Streams are perfect for these sort of problems.

Forecast highest = forecasts.stream()
                            .max((fc1, fc2) -> fc1.getTemp() - fc2.getTemp())
                            .get();

Answer 2

Another solution is use map reduce:

Optional<Forecast> element = forecasts
                     .stream()
                     .reduce((a,b) -> a.getTemperature() > b.getTemperature() ? a : b );

In this way you could even use use parallelStream()

Answer 3

I have two ideas. First of all, you used forecast in the parameter, but it should be forecasts. Also, you never gave your code for the class Forecast. I may be wrong, because I didn't see all of your code, but you need to convert Forecast to a Integer. Do this by Integer i = Integer.parseInt(forecasts); Next use Collections.max(i)

Answer 4

As your ArrayList contains Forecast objects you'll need to define how the max method should find the maximum element within your ArrayList.

something along the lines of this should work:

ArrayList<Forecast> forecasts = new ArrayList<>();
// Forecast object which has highest temperature
Forecast element = Collections.max(forecasts, Comparator.comparingInt(Forecast::getTemperature));
// retrieve the maximum temperature
int maxTemperature = element.getTemperature();

Answer 5

here is the simple method that return a max value from arraylist

public static object GetMaxValue(ArrayList arrayList)

{

 ArrayList sortArrayList= arrayList;

 sortArrayList.Sort();

 sortArrayList.Reverse();

 return sortArrayList[0];

}