Fix listening on port 8080 Warning

appengine-java11/appengine-simple-jetty-main/src/main/java/com/example/appengine/demo/jettymain/Main.java

@@ -36,7 +36,11 @@ public static void main(String[] args) throws Exception {
     // Note: If you set this to port 0, a randomly available port will be
     // assigned. You can find the assigned port in the logs or programmatically
     // obtain it.
-    Server server = new Server(8080);
+    Server server = new Server(
+                System.getenv().containsKey("PORT")
+                ? Integer.parseInt(System.getenv().get("PORT"))
+                : 8080
+        );
 
     // The WebAppContext is the interface to provide configuration for a web
     // application. In this example, the context path is being set to "/" so

appengine-java11/custom-entrypoint/Main.java

@@ -24,7 +24,11 @@ public class Main {
 
   public static void main(String[] args) throws IOException {
     // Create an instance of HttpServer bound to port 8080.
-    HttpServer server = HttpServer.create(new InetSocketAddress(8080), 0);
+    HttpServer server = HttpServer.create(new InetSocketAddress(
+                System.getenv().containsKey("PORT")
+                ? Integer.parseInt(System.getenv().get("PORT"))
+                : 8080
+        ), 0);
 
     // Set root URI path.
     server.createContext("/", (var t) -> {

appengine-java11/http-server/src/main/java/com/example/appengine/Main.java

@@ -25,7 +25,11 @@ public class Main {
 
   public static void main(String[] args) throws IOException {
     // Create an instance of HttpServer with port 8080.
-    HttpServer server = HttpServer.create(new InetSocketAddress(8080), 0);
+    HttpServer server = HttpServer.create(new InetSocketAddress(
+                System.getenv().containsKey("PORT")
+                ? Integer.parseInt(System.getenv().get("PORT"))
+                : 8080
+        ), 0);
 
     // Set root URI path.
     server.createContext("/", (var t) -> {

appengine-java11/sparkjava-helloworld/src/main/java/com/example/appengine/sparkdemo/Main.java

@@ -22,7 +22,11 @@ public class Main {
 
   public static void main(String[] args) {
     // Starts the webapp on localhost:8080.
-    Spark.port(8080);
+    Spark.port(
+                System.getenv().containsKey("PORT")
+                ? Integer.parseInt(System.getenv().get("PORT"))
+                : 8080
+        );
     Spark.get("/", (req, res) -> "Hello World!");
   }
 }