9.2 initial commit

build.gradle

@@ -9,7 +9,7 @@ compileJava.options.encoding = 'UTF-8'
 
 project.ext.junitVersion = '5.3.1'
 
-mainClassName = '_9._1.ColorMixer'
+mainClassName = '_9._2.Lights'
 
 sourceCompatibility = 1.8
 

src/main/java/_9/_2/Lights.java

@@ -0,0 +1,90 @@
+package _9._2;
+
+import javafx.application.Application;
+import javafx.collections.ObservableList;
+import javafx.scene.Node;
+import javafx.scene.Scene;
+import javafx.scene.layout.GridPane;
+import javafx.scene.paint.Color;
+import javafx.scene.paint.Paint;
+import javafx.scene.shape.Rectangle;
+import javafx.stage.Stage;
+
+import java.util.Optional;
+
+public class Lights extends Application {
+
+	private static final int DEFAULT_SIZE = 4;
+	private static final int GAP = 2;
+	private static final Paint ON = Color.YELLOW;
+	private static final Paint OFF = Color.WHITE;
+
+	@Override
+	public void start(Stage primaryStage) throws Exception {
+		final int size = Optional.ofNullable(this.getParameters().getNamed().get("size"))
+				.map(Integer::parseInt).orElse(DEFAULT_SIZE);
+		GridPane grid = new GridPane();
+		Scene scene = new Scene(grid, 600, 600);
+		scene.setFill(Color.BLACK);
+		grid.setHgap(GAP);
+		grid.setVgap(GAP);
+		for(int x = 0; x < size; x++) {
+			for(int y = 0; y < size; y++) {
+				Rectangle rec = new Rectangle(150, 150);
+				rec.heightProperty().bind(scene.heightProperty().subtract(size * GAP).divide(size));
+				rec.widthProperty().bind(scene.widthProperty().subtract(size * GAP).divide(size));
+				rec.setFill(OFF);
+				grid.add(rec, x, y);
+			}
+		}
+		for(int x = 0; x < size; x++) {
+			for(int y = 0; y < size; y++) {
+				Rectangle rec = getNodeByRowColumnIndex(x, y, grid);
+				assert rec != null;
+				Rectangle up = getNodeByRowColumnIndex(x, y - 1, grid);
+				Rectangle down = getNodeByRowColumnIndex(x, y + 1, grid);
+				Rectangle left = getNodeByRowColumnIndex(x - 1, y, grid);
+				Rectangle right = getNodeByRowColumnIndex(x + 1, y, grid);
+				rec.setOnMouseClicked(event -> {
+					toggle(rec);
+					toggle(up);
+					toggle(down);
+					toggle(left);
+					toggle(right);
+				});
+			}
+		}
+
+		primaryStage.setScene(scene);
+		primaryStage.setTitle("Lights");
+		primaryStage.show();
+	}
+
+	private void toggle(Rectangle rec) {
+		if(rec == null) {
+			return;
+		}
+		Paint color = rec.getFill();
+		if(color == ON) {
+			rec.setFill(OFF);
+		} else if(color == OFF) {
+			rec.setFill(ON);
+		} else {
+			throw new IllegalStateException();
+		}
+	}
+
+	public static <T extends Node> T getNodeByRowColumnIndex(final int column, final int row, GridPane gridPane) {
+		ObservableList<Node> children = gridPane.getChildren();
+		for(Node node : children) {
+			if(GridPane.getRowIndex(node) == row && GridPane.getColumnIndex(node) == column) {
+				return (T) node;
+			}
+		}
+		return null;
+	}
+
+	public static void main(String[] args) {
+		launch(args);
+	}
+}