Add builder example

Yalun Qin · eaglesky · commit fa82332c253e · 2016-08-14T00:28:21.000-07:00
diff --git a/Ellipse.java b/Ellipse.java
@@ -0,0 +1,44 @@
+public class Ellipse extends Shape {
+	public final float majorRadius;
+	public final float minorRadius;
+
+	private Ellipse(Color color, String name, float majorRadius, float minorRadius) {
+		super(color, name);
+		this.majorRadius = majorRadius;
+		this.minorRadius = minorRadius;
+	}
+
+	public static class Builder extends Shape.Builder<Ellipse.Builder> {
+		private float majorRadius;
+		private float minorRadius;
+
+		public Builder majorRadius(float majorRadius) {
+			this.majorRadius = majorRadius;
+			return this;
+		}
+
+		public Builder minorRadius(float minorRadius) {
+			this.minorRadius = minorRadius;
+			return this;
+		}
+
+		@Override
+		public Ellipse build() {
+			return new Ellipse(
+				this.color,
+				this.name,
+				this.majorRadius,
+				this.minorRadius);
+		}
+	}
+
+	@Override
+	public String toString() {
+		return "Ellipse: name = " + name
+				+ ", color = " + color
+				+ ", major radius = " + majorRadius
+				+ ", minor radius = " + minorRadius;
+	}
+	
+	
+}
diff --git a/Rectangle.java b/Rectangle.java
@@ -0,0 +1,43 @@
+public class Rectangle extends Shape {
+	public final float height;
+	public final float width;
+
+	private Rectangle(Color color, String name, float height, float width) {
+		super(color, name);
+		this.height = height;
+		this.width = width;
+	}
+
+	public static class Builder extends Shape.Builder<Rectangle.Builder> {
+		private float height;
+		private float width;
+
+		public Builder height(float height) {
+			this.height = height;
+			return this;
+		}
+
+		public Builder width(float width) {
+			this.width = width;
+			return this;
+		}
+
+		@Override
+		public Rectangle build() {
+			return new Rectangle(
+				this.color,
+				this.name,
+				this.height,
+				this.width);
+		}
+	}
+
+	@Override
+	public String toString() {
+		return "Rectangle: name = " + name
+				+ ", color = " + color
+				+ ", height = " + height
+				+ ", width = " + width;
+	}
+
+}
diff --git a/Shape.java b/Shape.java
@@ -0,0 +1,30 @@
+public abstract class Shape {
+	public final Color color;
+	public final String name;
+
+	public static enum Color {
+		RED, YELLOW, BLUE
+	}
+
+	protected Shape(Color color, String name) {
+		this.color = color;
+		this.name = name;
+	}
+
+	public static abstract class Builder<SB extends Builder<SB>> {
+		protected Color color;
+		protected String name;
+
+		public SB color(Color color) {
+			this.color = color;
+			return (SB) this;
+		}
+
+		public SB name(String name) {
+			this.name = name;
+			return (SB) this;
+		}
+
+		abstract Shape build();
+	}
+}
diff --git a/ShapeBuildersTest.java b/ShapeBuildersTest.java
@@ -0,0 +1,21 @@
+public class ShapeBuildersTest {
+
+	public static void main(String[] args) {
+		Ellipse.Builder ellipseBuilder = new Ellipse.Builder();
+		ellipseBuilder.majorRadius(3)
+					  .color(Shape.Color.BLUE)
+					  .name("Ellipse1")
+					  .minorRadius(1);
+		Ellipse ellipse = ellipseBuilder.build();
+		System.out.println(ellipse);
+		
+		Shape.Builder<Rectangle.Builder> rectangleBuilder = new Rectangle.Builder();
+		//Call the setters -- order matters, setters of Shape.Builder must come first!
+		rectangleBuilder.color(Shape.Color.RED)
+						.name("Rectangle1")
+						.height(2.3f)
+						.width(5.6f);
+		Shape shapeRectangle = rectangleBuilder.build();
+		System.out.println(shapeRectangle);
+	}
+}
