update,

it114105/itp3914/Lab11/ques_source/Ex1_Ex2/Circle.java

@@ -0,0 +1,11 @@
+class Circle {
+	private double radius;
+ 
+	public Circle(double r) {
+		radius = r;
+	}
+ 
+	public double area() {
+		return radius*radius*Math.PI;
+	}
+}

it114105/itp3914/Lab11/ques_source/Ex1_Ex2/Ex1.java

@@ -0,0 +1,33 @@
+class Circle {
+	private double radius;
+ 
+	public Circle(double r) {
+		radius = r;
+	}
+ 
+	public double area() {
+		return radius*radius*Math.PI;
+	}
+}
+
+class Rectangle {    
+    private double length;     
+    private double width;
+    public Rectangle(double l, double w)  {
+         length = l;        
+         width = w;    
+    }
+    public double area()  {        
+         return length * width;    
+    } 
+}
+
+public class Ex1 {
+	public static void main(String [] args) {
+		Rectangle r = new Rectangle(30.1, 10.2);
+		Circle c = new Circle(5.3);
+ 
+		System.out.println("r=" + r);
+		System.out.println("c=" + c);
+	}
+}	

it114105/itp3914/Lab11/ques_source/Ex1_Ex2/Ex2.java

@@ -0,0 +1,15 @@
+public class Ex2 {
+	public static void main(String [] args) {
+		Rectangle r = new Rectangle(1, 2);
+		System.out.println("r=" + r);
+		System.out.println("area=" + r.area());
+ 
+		r = new Rectangle(3, 4);
+		System.out.println("r=" + r);
+		System.out.println("area=" + r.area());
+ 
+		r = null;
+		System.out.println("r=" + r);
+		System.out.println("area=" + r.area());
+	}
+}

it114105/itp3914/Lab11/ques_source/Ex1_Ex2/Rectangle.java

@@ -0,0 +1,11 @@
+class Rectangle {    
+    private double length;     
+    private double width;
+    public Rectangle(double l, double w)  {
+         length = l;        
+         width = w;    
+    }
+    public double area()  {        
+         return length * width;    
+    } 
+}