fix string

src/backend/Board.java

@@ -106,22 +106,21 @@ public class Board {
 	}
 	
 	public String toString() {
-		ArrayList<String> ps=new ArrayList<>();
-		for(int y=0;y<lNum;y++) {
-			for (int x=0; x<cNum; x++) {
-				if (selectedCell != null) {
-				    ps.add(selectedCell.isWhite() ? "W" : "B");
-				    ps.add(selectedCell.getType().toString());
-				}
-				else {
-					ps.add("--");
-				}
-				ps.add(" ");
-			}
-			ps.add("\n");
-		}
-		return ps.toString();
+	    StringBuilder sb = new StringBuilder();
+	    for (int y = 0; y < lNum; y++) {
+	        for (int x = 0; x < cNum; x++) {
+	            Piece p = cells[x][y];
+	            if (p != null) {
+	                sb.append(p.isWhite() ? "W" : "B").append(p.getType().toString().charAt(0)).append(" ");
+	            } else {
+	                sb.append("-- ");
+	            }
+	        }
+	        sb.append("\n");
+	    }
+	    return sb.toString();
 	}
+
 	
 	public ArrayList<Piece> getPieces() {
 	    ArrayList<Piece> pieces = new ArrayList<>();