completed the solution for tasl 1.1

src/main/java/l_1/Bedroom.java

@@ -13,17 +13,10 @@ package l_1;
  *
  */
 
-public class Bedroom implements Room {
-
-	private double area = 0.0;
+public class Bedroom extends Room {
 
 	public Bedroom(double area) {
-		this.area = area;
-	}
-
-	@Override
-	public double getArea() {
-		return this.area;
+		super(area);
 	}
 
 }
\ No newline at end of file

src/main/java/l_1/DiningRoom.java

 package l_1;
 
-public class DiningRoom implements Room {
- 	private double area = 0.0;
+public class DiningRoom extends Room {
 
 	public DiningRoom(double area) {
-		this.area = area;
-	}
-
-
-	@Override
-	public double getArea() {
-		return this.area;
-	}
+		super(area);
+	} 
 
 }

src/main/java/l_1/Lounge.java

@@ -13,17 +13,11 @@ package l_1;
  *
  */
 
-public class Lounge implements Room {
-
-	private double area = 0.0;
+public class Lounge extends Room {
 
 	public Lounge(double area) {
-		this.area = area;
-	}
-
-	@Override
-	public double getArea() {
-		return this.area;
+		super(area);
 	}
 
+	
 }
\ No newline at end of file

src/main/java/l_1/Room.java

@@ -8,12 +8,20 @@ package l_1;
  *
  */
 
-public interface Room {
+public abstract class Room {
     
+	private double area = 0.0;
+    
+	public Room(double area) {
+		this.area = area;
+	}
+	
 	/**
 	 * Gets the area of a room.
 	 * @param void. 
 	 * @return double.
 	 */
-	public double getArea();
+	public double getArea() {
+		return this.area;
+	}
 }