ColorGrid.java

package prog2;

import java.util.LinkedList;
import java.util.Random;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.HPos;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.RadioButton;
import javafx.stage.Stage;
import javafx.scene.control.ToggleGroup;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Paint;
import javafx.scene.shape.StrokeType;

/**
 * VBox with built in style
 *
 * @author damiano
 */
class Sidebar extends VBox {

    public Sidebar(Node... nodes) {
        super(nodes);
        setSpacing(10);
        setPadding(new Insets(10));
        setStyle("-fx-background-color: #EEEEEE;");
    }
}

class CoordsRectangle extends Rectangle {

    int i, j;

    public CoordsRectangle(int i, int j, double d, Paint paint, double strokeSize) {
        super(d, d, paint);
        this.i = i;
        this.j = j;

        setStroke(Color.RED);
        setStrokeWidth(strokeSize);
        setStrokeType(StrokeType.CENTERED);
    }

}

class RectGridPane extends GridPane {

    static int gridSize = 8;
    double strokeSize = 2.0;
    double rectSize = 50.0;
    CoordsRectangle mx[][] = new CoordsRectangle[gridSize][gridSize];

    public RectGridPane() {
        setAlignment(Pos.CENTER);

        for (int i = 0; i < gridSize; ++i) {
            for (int j = 0; j < gridSize; ++j) {
                CoordsRectangle rect = new CoordsRectangle(i, j, rectSize, Color.WHITE, strokeSize);
                addCoordsRectangle(rect);
                GridPane.setHalignment(rect, HPos.CENTER);
            }
        }
    }

    CoordsRectangle removeCoordsRectangle(int i, int j) {
        CoordsRectangle rect = mx[i][j];
        getChildren().remove(rect);
        return rect;
    }

    void addCoordsRectangle(CoordsRectangle r) {
        mx[r.i][r.j] = r;
        add(r, r.i, r.j);
    }

}

class ChangeColorEventHandler implements EventHandler<MouseEvent> {

    LinkedList<Color> colorsList = new LinkedList<>();
    Rectangle r;

    public ChangeColorEventHandler(Rectangle r) {
        this.r = r;
        colorsList.add(Color.GREEN);
        colorsList.add(Color.BLUE);
        colorsList.add(Color.MAGENTA);
        colorsList.add(Color.NAVAJOWHITE);
    }

    @Override
    public void handle(MouseEvent t) {
        colorsList.addLast(colorsList.removeFirst());
        r.setFill(colorsList.getFirst());
    }
}

class RandomMoveEventHandler implements EventHandler<MouseEvent> {

    Random rand = new Random();
    RectGridPane grid;
    CoordsRectangle r;

    public RandomMoveEventHandler(CoordsRectangle r, RectGridPane grid) {
        this.r = r;
        this.grid = grid;
    }

    @Override
    public void handle(MouseEvent t) {
        int i, j, itmp, jtmp;
        CoordsRectangle r2;
        do {
            i = rand.nextInt(RectGridPane.gridSize);
            j = rand.nextInt(RectGridPane.gridSize);
        } while (i == r.i && j == r.j);
        r2 = grid.removeCoordsRectangle(i, j);
        grid.getChildren().remove(r);

        itmp = r2.i;
        jtmp = r2.j;
        r2.i = r.i;
        r2.j = r.j;
        r.i = itmp;
        r.j = jtmp;

        grid.addCoordsRectangle(r);
        grid.addCoordsRectangle(r2);
    }
}

public class ColorGrid extends Application {

    BorderPane root = new BorderPane();
    Label label = new Label("Select mode:");
    RadioButton radioColor = new RadioButton("Change color");
    RadioButton radioMove = new RadioButton("Random movevent");
    ToggleGroup toogleGroup = new ToggleGroup();
    Sidebar sidebar = new Sidebar(label, radioColor, radioMove);
    RectGridPane grid = new RectGridPane();

    CoordsRectangle colorRect;
    ChangeColorEventHandler changeColor;
    RandomMoveEventHandler randomMove;

    @Override
    public void start(Stage primaryStage) {
        colorRect = grid.mx[0][0];

        radioColor.setToggleGroup(toogleGroup);
        radioColor.setSelected(true);
        radioColor.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent t) {
                colorRect.setOnMouseClicked(changeColor);
            }
        });
        radioMove.setToggleGroup(toogleGroup);
        radioMove.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent t) {
                colorRect.setOnMouseClicked(randomMove);
            }
        });

        changeColor = new ChangeColorEventHandler(colorRect);
        colorRect.setFill(changeColor.colorsList.getFirst());
        randomMove = new RandomMoveEventHandler(colorRect, grid);
        colorRect.setOnMouseClicked(changeColor);

        root.setLeft(sidebar);
        root.setCenter(grid);

        primaryStage.setScene(new Scene(root, 600, 470));
        primaryStage.setMinHeight(470);
        primaryStage.setMinWidth(600);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}