import javafx.scene.canvas.GraphicsContext;
import javafx.scene.paint.Color;

import java.io.IOException;
import java.util.HashMap;

/**
 * Created by TUDelft SID on 8-5-2017.
 */
public class GraphDrawer {

    private int Xsize = 10;
    private int Ysize = 6;
    private int lengthEdge = 2;
    private int yBase = 40;

    private SequenceGraph graph;
    private GraphicsContext gc;

    public GraphDrawer(SequenceGraph graph, GraphicsContext gc) {
        this.graph = graph;
        this.gc = gc;
        graph.initialize();
        graph.layerizeGraph();
    }

    public void drawShapes() throws IOException {
        HashMap<Integer, SequenceNode> nodes = graph.getNodes();

        for(int i = 1; i <= nodes.size(); i++) {
            SequenceNode node = nodes.get(i);
            gc.setFill(Color.BLUE);
            gc.fillRoundRect((node.getColumn() * (Xsize + lengthEdge)) + 50, yBase, Xsize, Ysize, 10, 10);
//            gc.setStroke(Color.BLACK);
//            gc.setLineWidth(1);
//            gc.strokeLine((node.getColumn() * (Xsize + lengthEdge)) + Xsize + 50,43, node.getColumn() * (Xsize + Xsize + lengthEdge) + 50, 43);
        }
    }
}


@@ -210,24 +210,37 @@
    p
-rivate
+ublic static final
  int X
-size
+_SIZE
  = 1
@@ -251,24 +251,37 @@
    p
-rivate
+ublic static final
  int Y
-size
+_SIZE
  = 6
@@ -291,56 +291,82 @@
    p
-rivate int lengthEdge = 2;%0A    private int yBase
+ublic static final int EDGE_LENGTH = 2;%0A    public static final int Y_BASE
  = 4
@@ -919,53 +919,58 @@
 * (X
-size + lengthEdge)) + 50, yBase, Xsize, Ysize
+_SIZE + EDGE_LENGTH)) + 50, Y_BASE, X_SIZE, Y_SIZE
 , 10

Use final number instead of magic numbers