Find nth Largest elements from Integer List using Java Stream

By Atul Rai | Last Updated: July 30, 2023 Previous       Next

To find the nth highest elements from an integer list using Java 8 Stream API, you can follow these steps:

1. Sort the integer list in descending order.
2. Take the first n elements from the sorted list.

1. Find Single Element

public static Integer findNthHighestElement(List<Integer> integerList, int n) {

        if (integerList.isEmpty() || n <= 0 || integerList.size() < n)
            throw new IllegalArgumentException("Please validate your inputs.");

        return integerList.stream()
                .distinct()
                .sorted(Collections.reverseOrder())
                .collect(Collectors.toList()).get(n - 1);
    }

2. Find All Elements

To find all occurrences of the third highest elements in the list, you can modify the code to keep track of the third highest element and then filter all elements that are equal to it.

public static List<Integer> findAllNthHighestElements(List<Integer> integerList, int n) {

        if (integerList.isEmpty() || n <= 0 || integerList.size() < n)
            throw new IllegalArgumentException("Please validate your inputs.");

        Integer highestElement = integerList.stream()
                .distinct()
                .sorted(Collections.reverseOrder())
                .collect(Collectors.toList()).get(n - 1);

        return integerList.stream()
                .filter(e -> e == highestElement)
                .collect(Collectors.toList());
    }

Here is the complete example.

package org.websparrow;

import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;

public class FindNthElements {

    public static void main(String[] args) {

        List<Integer> integerList = Arrays.asList(10, 20, 5, 15, 30, 25, 20);
        int n = 3; // Change n to get the nth highest elements

        Integer highestElement = findNthHighestElement(integerList, n);
        System.out.println("The " + n + " highest element is: " + highestElement);

        List<Integer> allHighestElements = findAllNthHighestElements(integerList, n);
        System.out.println("The " + n + " highest elements are: " + allHighestElements);
    }

    public static Integer findNthHighestElement(List<Integer> integerList, int n) {

        if (integerList.isEmpty() || n <= 0 || integerList.size() < n)
            throw new IllegalArgumentException("Please validate your inputs.");

        return integerList.stream()
                .distinct()
                .sorted(Collections.reverseOrder())
                .collect(Collectors.toList()).get(n - 1);
    }

    public static List<Integer> findAllNthHighestElements(List<Integer> integerList, int n) {

        if (integerList.isEmpty() || n <= 0 || integerList.size() < n)
            throw new IllegalArgumentException("Please validate your inputs.");

        Integer highestElement = integerList.stream()
                .distinct()
                .sorted(Collections.reverseOrder())
                .collect(Collectors.toList()).get(n - 1);

        return integerList.stream()
                .filter(e -> e == highestElement)
                .collect(Collectors.toList());
    }
}

Output:

The 3 highest element is: 20
The 3 highest elements are: [20, 20]

References

1. Java 8- Find the nth Highest Salary
2. Java 8 – Find Non Duplicate Elements from List