Observer Design Pattern - Bonus example - Java api implementation

premaseem · premaseem · commit ffdbcab0bef4 · 2018-03-12T14:55:18.000-05:00
diff --git a/patternBonus/src/com/premaseem/ClientJavaApi.java b/patternBonus/src/com/premaseem/ClientJavaApi.java
@@ -0,0 +1,54 @@
+package com.premaseem;
+/*
+@author: Aseem Jain
+@title: Design Patterns with Java 9
+@link: https://premaseem.wordpress.com/category/computers/design-patterns/
+*/
+
+import java.util.Observable;
+import java.util.Observer;
+import java.util.Scanner;
+
+public class ClientJavaApi {
+
+    public static void main(String[] args) {
+
+        // Created subject
+        Subject subject = new Subject();
+
+        // Created Observer
+        Observer observer = new Observer() {
+            public void update(Observable obj, Object arg) {
+                System.out.println("Observer notified with update: " + arg);
+            }
+        };
+
+        // registered observer to the subject
+        subject.addObserver(observer);
+
+        System.out.println("Make text updates in subject: ");
+        new Thread(subject).start();
+    }
+}
+
+class Subject extends Observable implements Runnable {
+    public void run() {
+
+        // Every time whenever there is an update in subject,
+        // observer will be notified
+        while (true) {
+            String update = new Scanner(System.in).next();
+            setChanged();
+            notifyObservers(update);
+        }
+    }
+}
+
+/** Lesson Learnt
+ *
+ *  1. Instead of creating our own observer and observable,
+ *  using (java.util) Java api's  implementation of observer and observable
+ *
+ *  2. Java 9 has deprecated above apis, WHY ?
+ *  answer is in link -https://stackoverflow.com/questions/46380073/observer-is-deprecated-in-java-9-what-should-we-use-instead-of-it
+ * */
