mutable and immutable cells

app/src/main/java/sudoku/Cell.java

@@ -1,10 +1,10 @@
 package sudoku;
 
-public class Cell {
+public abstract class Cell {
 
-	private static int NOSYMBOLE = -1;
+	protected static int NOSYMBOLE = -1;
-	private int symboleIndex;
+	protected int symboleIndex;
-	private Block block = null;
+	protected Block block = null;
 
 	public Cell(int symboleIndex) {
 		this.symboleIndex = symboleIndex;
@@ -21,14 +21,6 @@ public class Cell {
 		return symboleIndex;
 	}
 
-	public void setSymboleIndex(int symboleIndex) {
-		this.symboleIndex = symboleIndex;
-	}
-
-	public void clear() {
-		setSymboleIndex(NOSYMBOLE);
-	}
-
 	public Block getBlock() {
 		return this.block;
 	}

app/src/main/java/sudoku/ImmutableCell.java

@@ -0,0 +1,9 @@
+package sudoku;
+
+public class ImmutableCell extends Cell {
+
+	public ImmutableCell(int symboleIndex) {
+		super(symboleIndex);
+	}
+
+}

app/src/main/java/sudoku/MutableCell.java

@@ -0,0 +1,32 @@
+package sudoku;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class MutableCell extends Cell{
+
+	private final List<Integer> hintsSymbolIndex;
+
+	public MutableCell() {
+		super();
+		this.hintsSymbolIndex = new ArrayList<>();
+	}
+
+	public MutableCell(int symboleIndex) {
+		super(symboleIndex);
+		this.hintsSymbolIndex = new ArrayList<>();
+	}
+
+	public void setSymboleIndex(int symboleIndex) {
+		this.symboleIndex = symboleIndex;
+	}
+
+	public void clear() {
+		setSymboleIndex(NOSYMBOLE);
+	}
+
+	public List<Integer> getHints() {
+		return this.hintsSymbolIndex;
+	}
+
+}

app/src/main/java/sudoku/SudokuFactory.java

@@ -8,7 +8,7 @@ public class SudokuFactory {
 	private static List<Cell> initCells(int size) {
 		List<Cell> cells = new ArrayList<>(size * size);
 		for (int i = 0; i < size * size; i++) {
-			cells.add(new Cell());
+			cells.add(new MutableCell());
 		}
 		return cells;
 	}