diff --git a/Chapter7/Dynamic_Disptach_Demo_2.java b/Chapter7/Dynamic_Disptach_Demo_2.java
new file mode 100644
index 0000000..9babea9
--- /dev/null
+++ b/Chapter7/Dynamic_Disptach_Demo_2.java
@@ -0,0 +1,19 @@
+
+public class Dynamic_Disptach_Demo_2 {
+
+	public static void main(String[] args) {
+		
+		Sup superOb = new Sup();
+
+		superOb.who();       // In each case, the version of who() to call is determined at run time by ...
+		
+		superOb = new Sub1();
+		superOb.who();       // ... the type of object being referred to.
+		
+		superOb = new Sub2();
+		superOb.who();
+		
+
+	}
+
+}
diff --git a/Chapter7/SupSubRef2.java b/Chapter7/SupSubRef2.java
new file mode 100644
index 0000000..3a9a0a3
--- /dev/null
+++ b/Chapter7/SupSubRef2.java
@@ -0,0 +1,41 @@
+// A superclass reference can refer to a subclass object. 
+
+class X3 {
+	int a;
+	
+	public X3(int i) {
+		// TODO Auto-generated constructor stub
+		
+		a = i;
+	}
+}
+
+class Y3 extends X3 {
+	int b;
+	
+	public Y3(int i, int j) {
+		// TODO Auto-generated constructor stub
+		super(j);
+		b = i;
+	}
+}
+
+public class SupSubRef2 {
+
+	public static void main(String[] args) {
+		
+		X3 x3 = new X3(10);
+		Y3 y3 = new Y3(5, 6);
+		
+		System.out.println("X.a: " + x3.a);
+		
+		x3 = y3; 
+		System.out.println("X.a: " + x3.a);
+		
+		// X references know only about X members
+		x3.a = 19;  // OK
+// 		x3.b = 27;  // Error, X does not have a b member. 
+
+	}
+
+}
diff --git a/Miscellaneous/L4_Civil_Servant_Admission_Exam/Intro_to_CS_No17_2026.java b/Miscellaneous/L4_Civil_Servant_Admission_Exam/Intro_to_CS_No17_2026.java
new file mode 100644
index 0000000..3ea27b6
--- /dev/null
+++ b/Miscellaneous/L4_Civil_Servant_Admission_Exam/Intro_to_CS_No17_2026.java
@@ -0,0 +1,29 @@
+package L4_Civil_Servant_Admission_Exam;
+
+public class Intro_to_CS_No17_2026 {
+
+	public static void main(String[] args) {
+		
+		int month = 1;
+		
+		while(month <= 4) {
+			
+			switch(month) { 
+			
+			case 1: 
+				System.out.println("31");
+			
+			case 2:
+				System.out.println("28");
+				
+			case 4:
+				System.out.println("30");
+			
+			}
+			
+			month++;
+		}
+
+	}
+
+}