remove "instanceof Pawn"

app/src/main/java/chess/model/visitor/KingIdentifier.java

@@ -1,6 +1,7 @@
 package chess.model.visitor;
 
 import chess.model.Color;
+import chess.model.Piece;
 import chess.model.PieceVisitor;
 import chess.model.pieces.*;
 
@@ -12,6 +13,12 @@ public class KingIdentifier implements PieceVisitor<Boolean> {
 		this.color = color;
 	}
 
+	public boolean isKing(Piece piece) {
+		if (piece == null)
+			return false;
+		return visit(piece);
+	}
+
 	@Override
 	public Boolean visitPiece(Bishop bishop) {
 		return false;

app/src/main/java/chess/model/visitor/PawnIdentifier.java

@@ -0,0 +1,52 @@
+package chess.model.visitor;
+
+import chess.model.Color;
+import chess.model.Piece;
+import chess.model.PieceVisitor;
+import chess.model.pieces.*;
+
+public class PawnIdentifier implements PieceVisitor<Boolean> {
+
+	private final Color color;
+
+	public PawnIdentifier(Color color) {
+		this.color = color;
+	}
+
+	public boolean isPawn(Piece piece) {
+		if (piece == null)
+			return false;
+		return visit(piece);
+	}
+
+	@Override
+	public Boolean visitPiece(Bishop bishop) {
+		return false;
+	}
+
+	@Override
+	public Boolean visitPiece(King king) {
+		return false;
+	}
+
+	@Override
+	public Boolean visitPiece(Knight knight) {
+		return false;
+	}
+
+	@Override
+	public Boolean visitPiece(Pawn pawn) {
+		return pawn.getColor() == color;
+	}
+
+	@Override
+	public Boolean visitPiece(Queen queen) {
+		return false;
+	}
+
+	@Override
+	public Boolean visitPiece(Rook rook) {
+		return false;
+	}
+
+}