Example: List Equality Using Frequency Maps in Java

// List Equality Using Frequency Maps
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

// Main class containing the entry point of the program
public class Main {

    /**
     * Helper method to create a frequency map for a given list.
     * @param list The list to create a frequency map from.
     * @return A map where keys are list elements and values are their counts.
     */
    private static <T> Map<T, Integer> createFrequencyMap(List<T> list) {
        Map<T, Integer> frequencyMap = new HashMap<>();
        for (T item : list) {
            frequencyMap.put(item, frequencyMap.getOrDefault(item, 0) + 1);
        }
        return frequencyMap;
    }

    public static void main(String[] args) {
        // Step 1: Create lists with varying elements and duplicates
        List<String> listX = new ArrayList<>(Arrays.asList("A", "B", "A", "C"));
        List<String> listY = new ArrayList<>(Arrays.asList("A", "C", "B", "A"));
        List<String> listZ = new ArrayList<>(Arrays.asList("A", "B", "C")); // Fewer duplicates
        List<String> listW = new ArrayList<>(Arrays.asList("A", "B", "A", "D")); // Different element

        System.out.println("Original listX: " + listX);
        System.out.println("Original listY: " + listY);
        System.out.println("Original listZ: " + listZ);
        System.out.println("Original listW: " + listW);

        // Step 2: Create frequency maps for each list
        Map<String, Integer> freqMapX = createFrequencyMap(listX);
        Map<String, Integer> freqMapY = createFrequencyMap(listY);
        Map<String, Integer> freqMapZ = createFrequencyMap(listZ);
        Map<String, Integer> freqMapW = createFrequencyMap(listW);

        System.out.println("\nFrequency Map for listX: " + freqMapX);
        System.out.println("Frequency Map for listY: " + freqMapY);
        System.out.println("Frequency Map for listZ: " + freqMapZ);
        System.out.println("Frequency Map for listW: " + freqMapW);

        // Step 3: Compare the frequency maps using Map.equals()
        boolean areEqualXAndY = freqMapX.equals(freqMapY);
        boolean areEqualXAndZ = freqMapX.equals(freqMapZ);
        boolean areEqualXAndW = freqMapX.equals(freqMapW);

        System.out.println("\nAre listX and listY equal (using frequency maps)? " + areEqualXAndY);
        System.out.println("Are listX and listZ equal (using frequency maps)? " + areEqualXAndZ);
        System.out.println("Are listX and listW equal (using frequency maps)? " + areEqualXAndW);
    }
}