Fixed maps.

chess/src/chess/Board.java

@@ -1,5 +1,6 @@
 package chess;
 import java.awt.Color;
+import java.util.HashMap;
 import java.util.Map;
 import javalib.impworld.WorldScene;
 import javalib.worldimages.EmptyImage;
@@ -10,6 +11,8 @@ import javalib.worldimages.RectangleImage;
 class Board {
     Map<Coord, Piece> board;
 
+    Board() { this.board = new HashMap<Coord, Piece>(); }
+
     WorldScene draw() {
         WorldScene scene =
             new WorldScene(Util.boardW * Util.scale, Util.boardW * Util.scale);
@@ -31,6 +34,9 @@ class Board {
 
         return scene;
     }
+
+    void set(Coord coord, Piece piece) { this.board.put(coord, piece); }
+    Piece get(Coord coord) { return this.board.get(coord); }
 }
 
 // Measured from top left.
@@ -51,11 +57,10 @@ class Coord {
     }
 
     // Whether two Coords are equal.
-    public Boolean equals(Coord that) {
-        return this.x == that.x && this.y == that.y;
+    public boolean equals(Object that) {
+        if (!(that instanceof Coord)) return false;
+        else return ((Coord)that).x == this.x && ((Coord)that).y == this.y;
     }
 
-    public int hashCode() {
-        return 31 * Integer.hashCode(this.x) + Integer.hashCode(this.y);
-    }
+    public int hashCode() { return 31 * Integer.hashCode(this.x + this.y); }
 }

chess/src/chess/Main.java

@@ -4,4 +4,20 @@ import tester.Tester;
 
 class Examples {
     void testItAll(Tester t) { new Game().run(); }
+    void testCoord(Tester t) {
+        Coord coord = new Coord(1, 1);
+        Coord cod = new Coord(1, 1);
+        Coord cor = new Coord(1, 2);
+        t.checkExpect(coord.equals(cod), true);
+        t.checkExpect(coord.equals(cor), false);
+        t.checkExpect(coord.hashCode() == cod.hashCode(), true);
+        t.checkExpect(coord.hashCode() == cor.hashCode(), false);
+    }
+
+    void testBoard(Tester t) {
+        Piece pawn = new Pawn();
+        Board board = new Board();
+        board.set(new Coord(0, 0), pawn);
+        t.checkExpect(board.get(new Coord(0, 0)), pawn);
+    }
 }