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;
-	private int symboleIndex;
-	private Block block = null;
+	protected static int NOSYMBOLE = -1;
+	protected int symboleIndex;
+	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;
 	}