In Java, to draw a rectangle (outlines) onto the current graphics context, we can use the following methods provided by the Graphics/Graphics2D class:

• drawRect(int x, int y, int width, int height)
• draw3DRect(int x, int y, int width, int height, boolean raised)
• draw(Rectangle2D)
• drawRoundRect(int x, int y, int width, int height, int arcWidth, int arcHeight)

With:

• (x, y) is the upper left corner of the rectangle.
• width and height: specify dimension of the rectangle.
• raised: specifies whether the rectangle edges are raised or sunk when drawing a 3D rectangle.
• Rectangle2D is the base class of Rectangle (for integer coordinates) Rectangle2D.Double (for double coordinates) and Rectangle2D.Float (for float coordinates).
• arcWidth and arcHeight: specify the horizontal and vertical diameters of the arcs at the four corners when drawing a rectangle with rounded corners.

To demonstrate the examples, we create the following Swing program:

/**
 * This program demonstrates how to rectangles using Graphics2D object.
 * @author www.codejava.net
 *
 */
public class RectanglesDrawingExample extends JFrame {

	public RectanglesDrawingExample() {
		super("Rectangles Drawing Demo");

		getContentPane().setBackground(Color.WHITE);
		setSize(480, 200);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setLocationRelativeTo(null);
	}

	void drawRectangles(Graphics g) {
		Graphics2D g2d = (Graphics2D) g;

		// code to draw rectangles goes here...

	}

	public void paint(Graphics g) {
		super.paint(g);
		drawRectangles(g);
	}

	public static void main(String[] args) throws Exception {

		SwingUtilities.invokeLater(new Runnable() {
			@Override
			public void run() {
				new RectanglesDrawingExample().setVisible(true);
			}
		});
	}
}

The code examples will go into the drawRectangles() method which obtains graphics context of the JFrame window:

void drawRectangles(Graphics g) {
	Graphics2D g2d = (Graphics2D) g;

	// code to draw rectangles goes here...

}

Now, let’s see the examples in details.

 

1. Drawing Rectangles in integer coordinates

Using the drawRect() method:

g2d.drawRect(30, 50, 420, 120);

Using the draw(Rectangle) method:

g2d.draw(new Rectangle(30, 50, 420, 120));

Result:

 

 

2. Drawing Rectangles in double coordinates

To draw a rectangle in double coordinates, create a new instance of the Rectangle2D.Double class. For example:

double x = 29.5d;
double y = 48.8d;
double width = 413.2d;
double height = 118.6d;

Rectangle2D.Double rect = new Rectangle2D.Double(x, y, width, height);
g2d.draw(rect);

Or like this for short:

g2d.draw(new Rectangle2D.Double(29.5d, 48.8d, 413.2d, 118.6d));

 

3. Drawing Rectangles in float coordinates

Similar to double coordinates, we use the Rectangle2D.Float class to draw rectangles in float coordinates. For example:

float x = 29.5f;
float y = 48.8f;
float width = 413.2f;
float height = 118.6f;

Rectangle2D.Float rect = new Rectangle2D.Float(x, y, width, height);
g2d.draw(rect);

Or like this for short:

g2d.draw(new Rectangle2D.Float(29.5f, 48.8f, 413.2f, 118.6f));

 

4. Drawing Rectangles with Rounded-Corners

To draw a rectangle with four rounded corners, use the drawRoundRect() method and pass values for the horizontal diameter (arcWidth) and vertical diameter (arcHeight) of the corners. Here’s an example:

int x = 30;
int y = 50;
int width = 420;
int height = 120;
int arcWidth = 20;
int arcHeight = 20;

g2d.drawRoundRect(x, y, width, height, arcWidth, arcHeight);

Result:

The following example plays around with various values for the arcWidth and arcHeight:

g2d.drawRoundRect(x, y, width, height, arcWidth, arcHeight);
g2d.drawRoundRect(x + 10, y + 10, width - 20, height - 20, arcWidth + 10, arcHeight + 10);
g2d.drawRoundRect(x + 20, y + 20, width - 40, height - 40, arcWidth + 20, arcHeight + 10);
g2d.drawRoundRect(x + 30, y + 30, width - 60, height - 60, arcWidth + 40, arcHeight + 20);

Result:

 

 

5. Drawing 3D Rectangles

The draw3DRect() method draws a rectangle with edges appear to be raised or sunk, specified by the raised boolean flag. Here’s an example:

int x = 30;
int y = 50;
int width = 420;
int height = 120;
boolean raised = true;

g2d.setColor(Color.LIGHT_GRAY);

g2d.draw3DRect(x, y, width, height, raised);

Result (a really simple 3D effect):

The following example draws two rectangles - one with raised edges and one with sunk edges:

g2d.setColor(Color.LIGHT_GRAY);
g2d.draw3DRect(30, 50, 200, 120, true);
g2d.draw3DRect(250, 50, 200, 120, false);

Result:

NOTE: The draw3DRect() method uses only the current color and ignores the current paint, such as line strokes.

 

6. Drawing Rectangles with Custom Strokes

Rather than using the default style (thin and solid line, black color), we can make some attractive decorations for the outlines of the rectangles using Strokes. For example:

Stroke stroke1 = new BasicStroke(6f);

g2d.setColor(Color.BLACK);
g2d.setStroke(stroke1);

g2d.drawRect(30, 50, 420, 120);

That draws a rectangle with outlines in blue color and thickness of 6 pixels width. Here’s the result:

To understand more about using strokes, see the tutorial: Drawing lines examples with Graphics2D. The following code snippet plays around with various strokes:

int x = 20;
int y = 40;
int width = 440;
int height = 140;

Stroke stroke1 = new BasicStroke(6f);

g2d.setColor(Color.BLUE);
g2d.setStroke(stroke1);
g2d.drawRect(x, y, width, height);

float[] dashingPattern1 = {2f, 2f};
Stroke stroke2 = new BasicStroke(2f, BasicStroke.CAP_BUTT,
		BasicStroke.JOIN_MITER, 1.0f, dashingPattern1, 2.0f);

g2d.setColor(Color.RED);
g2d.setStroke(stroke2);
g2d.drawRect(x + 20, y + 20, width - 40, height - 40);

float[] dashingPattern2 = {10f, 4f};
Stroke stroke3 = new BasicStroke(4f, BasicStroke.CAP_BUTT,
		BasicStroke.JOIN_MITER, 1.0f, dashingPattern2, 0.0f);

g2d.setColor(Color.GREEN);
g2d.setStroke(stroke3);
g2d.drawRect(x + 40, y + 40, width - 80, height - 80);


float[] dashingPattern3 = {10f, 10f, 1f, 10f};
Stroke stroke4 = new BasicStroke(4f, BasicStroke.CAP_SQUARE,
		BasicStroke.JOIN_MITER, 1.0f, dashingPattern3, 0.0f);

g2d.setColor(Color.BLUE);
g2d.setStroke(stroke4);
g2d.drawRect(x + 60, y + 60, width - 120, height - 120);

Result:

 

API References:

• drawRect() method Javadoc
• draw3DRect() method Javadoc
• draw(Shape) method Javadoc
• drawRoundRect() method Javadoc
• BasicStroke class Javadoc
• Rectangle2D class Javadoc
• Rectangle class Javadoc
• Rectangle2D.Double class Javadoc
• Rectangle2D.Float class Javadoc

 

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