import java.util.*;
import java.util.stream.Collectors;
 
class MatrixCommonElements {
 
    public static void main(String[] args) {
        int[][] matrix = {{7, 1, 3, 5, 3, 6},
                          {2, 3, 6, 1, 1, 6},
                          {6, 1, 7, 2, 1, 4},
                          {6, 6, 7, 1, 3, 3},
                          {5, 5, 6, 1, 5, 4},
                          {3, 5, 6, 2, 7, 1},
                          {4, 1, 4, 3, 6, 4},
                          {4, 6, 1, 7, 4, 3}};
 
        Set<Integer> commonElements = toSet(matrix[0]);
 
        for (int i = 1; i < matrix.length; i++) {
            commonElements.retainAll(toSet(matrix[i]));
        }
 
        System.out.println(commonElements);
    }
 
    private static Set<Integer> toSet(int[] intArray) {
        return Arrays.stream(intArray).boxed().collect(Collectors.toSet());
    }
 
}

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