java-泛型和内部类

Cell类应该是静态的吗？如果类型参数不需要是静态的，是否可以从外部类共享？

如有任何澄清，将不胜感激。

public class Matrix {
    private final int numberOfRows;
    private final int numberOfColumns;
    private final List<Cell> data;

    public Matrix(int numberOfRows, int numberOfColumns) {
        this.numberOfRows = numberOfRows;
        this.numberOfColumns = numberOfColumns;

        data = buildMatrix();
    }

    private List<Cell> buildMatrix() {
        return IntStream.range(0, numberOfRows * numberOfColumns)
                .mapToObj(i -> new Cell(i / numberOfColumns, i % numberOfColumns))
                .collect(Collectors.toUnmodifiableList());
    }

    public int getNumberOfRows() {
        return numberOfRows;
    }

    public int getNumberOfColumns() {
        return numberOfColumns;
    }

    public Cell get(int rowId, int columnId) {
        return get(rowId, columnId, cell -> cell.rowId == rowId && cell.columnId == columnId).get(0);
    }

    public List<Cell> getRow(int rowId) {
        return get(rowId, 0, cell -> cell.rowId == rowId);
    }

    public List<Cell> getColumn(int columnId) {
        return get(0, columnId, cell -> cell.columnId == columnId);
    }

    public List<Cell> getAscendingDiagonal(int rowId, int columnId) {
        return get(rowId, columnId, cell -> cell.rowId - rowId == cell.columnId - columnId);
    }

    public List<Cell> getDescendingDiagonal(int rowId, int columnId) {
        return get(rowId, columnId, cell -> cell.rowId - rowId == -(cell.columnId - columnId));
    }

    private List<Cell> get(int rowId, int columnId, Predicate<Cell> filter) {
        return data.stream()
                .filter(filter)
                .sequential()
                .collect(Collectors.toUnmodifiableList());
    }

    public void occupyCell(int rowId, int columnId, T t) {
        get(rowId, columnId).setOccupant(t);
    }

    public void reset() {
        data.forEach(Cell::clear);
    }

    static class Cell {
        private final int rowId;
        private final int columnId;
        private T occupant;

        private Cell(int rowId, int columnId) {
            this.rowId = rowId;
            this.columnId = columnId;
        }

        public Optional getOccupant() {
            return Optional.ofNullable(occupant);
        }

        public int getRowId() {
            return rowId;
        }

        public int getColumnId() {
            return columnId;
        }

        private void setOccupant(T t) {
            occupant = t;
        }

        private void clear() {
            occupant = null;
        }

        @Override
        public String toString() {
            return "Cell{" +
                    "rowId=" + rowId +
                    ", columnId=" + columnId +
                    ", occupant=" + occupant +
                    '}';
        }
    }
}