added chain of responsibility sample

chain/src/main/java/com/iluwatar/RequestHandler.java

@@ -0,0 +1,23 @@
+package com.iluwatar;
+
+public abstract class RequestHandler {
+	
+	private RequestHandler next;
+
+	public RequestHandler(RequestHandler next) {
+		this.next = next;
+	}
+	
+	public void handleRequest(Request req) {
+		if (next != null) {
+			next.handleRequest(req);
+		}
+	}
+
+	protected void printHandling(Request req) {
+		System.out.println(this + " handling request \"" + req + "\"");
+	}
+
+	@Override
+	public abstract String toString();
+}