diff --git a/em-oop/src/Day3Check2.java b/em-oop/src/Day3Check2.java
new file mode 100644
index 0000000..08aa5c4
--- /dev/null
+++ b/em-oop/src/Day3Check2.java
@@ -0,0 +1,11 @@
+
+public class Day3Check2 {
+	public static void main(String[] args) {
+		Rectangle rect = new Rectangle(3, 4);
+		rect.showInfo();
+		
+		Greeting greeting = new JapaneseGreeting();
+		System.out.println(greeting.hello());
+	}
+
+}
diff --git a/em-oop/src/Greeting.java b/em-oop/src/Greeting.java
new file mode 100644
index 0000000..09fe171
--- /dev/null
+++ b/em-oop/src/Greeting.java
@@ -0,0 +1,6 @@
+
+public interface Greeting {
+
+	String hello();
+
+}
diff --git a/em-oop/src/JapaneseGreeting.java b/em-oop/src/JapaneseGreeting.java
new file mode 100644
index 0000000..6d40cce
--- /dev/null
+++ b/em-oop/src/JapaneseGreeting.java
@@ -0,0 +1,8 @@
+
+public class JapaneseGreeting implements Greeting {
+	@Override
+	public String hello() {
+		return "こんにちは";
+	}
+
+}
diff --git a/em-oop/src/Rectangle.java b/em-oop/src/Rectangle.java
new file mode 100644
index 0000000..b2f6473
--- /dev/null
+++ b/em-oop/src/Rectangle.java
@@ -0,0 +1,17 @@
+
+public class Rectangle extends Shape{
+	private double width;
+	private double height;
+	
+	public Rectangle(double width, double height) {
+		super("四角形");
+		this.width = width;
+		this.height = height;
+	}
+	
+	@Override
+	public double area() {
+		return width * height;
+	}
+
+}
diff --git a/em-oop/src/Shape.java b/em-oop/src/Shape.java
index a1fc549..6eea310 100644
--- a/em-oop/src/Shape.java
+++ b/em-oop/src/Shape.java
@@ -1,16 +1,15 @@
 
-public class Shape {
+public abstract class Shape {
 	private String name;
+
 	public Shape(String name) {
 		this.name = name;
 	}
-	
-	public double area() {
-		return 0.0;
-	}
+
+	public abstract double area();
+
 	public void showInfo() {
 		System.out.println(this.name + "の面積は" + this.area() + "です");
 	}
-	
-	
+
 }