Added useful comments to the first example.

modules/cloudsim-examples/src/main/java/org/cloudbus/cloudsim/examples/CloudSimExample1.java

@@ -35,14 +35,11 @@ import org.cloudbus.cloudsim.provisioners.PeProvisionerSimple;
 import org.cloudbus.cloudsim.provisioners.RamProvisionerSimple;
 
 /**
- * A simple example showing how to create a datacenter with one host and run one
- * cloudlet on it.
+ * A simple example showing how to create a data center with one host and run one cloudlet on it.
  */
 public class CloudSimExample1 {
-
 	/** The cloudlet list. */
 	private static List<Cloudlet> cloudletList;
-
 	/** The vmlist. */
 	private static List<Vm> vmlist;
 
@@ -53,17 +50,33 @@ public class CloudSimExample1 {
 	 */
 	@SuppressWarnings("unused")
 	public static void main(String[] args) {
-
 		Log.printLine("Starting CloudSimExample1...");
 
 		try {
-			// First step: Initialize the CloudSim package. It should be called
-			// before creating any entities.
+			// First step: Initialize the CloudSim package. It should be called before creating any entities.
 			int num_user = 1; // number of cloud users
-			Calendar calendar = Calendar.getInstance();
-			boolean trace_flag = false; // mean trace events
-
-			// Initialize the CloudSim library
+			Calendar calendar = Calendar.getInstance(); // Calendar whose fields have been initialized with the current date and time.
+ 			boolean trace_flag = false; // trace events
+
+			/* Comment Start - Dinesh Bhagwat 
+			 * Initialize the CloudSim library. 
+			 * init() invokes initCommonVariable() which in turn calls initialize() (all these 3 methods are defined in CloudSim.java).
+			 * initialize() creates two collections - an ArrayList of SimEntity Objects (named entities which denote the simulation entities) and 
+			 * a LinkedHashMap (named entitiesByName which denote the LinkedHashMap of the same simulation entities), with name of every SimEntity as the key.
+			 * initialize() creates two queues - a Queue of SimEvents (future) and another Queue of SimEvents (deferred). 
+			 * initialize() creates a HashMap of of Predicates (with integers as keys) - these predicates are used to select a particular event from the deferred queue. 
+			 * initialize() sets the simulation clock to 0 and running (a boolean flag) to false.
+			 * Once initialize() returns (note that we are in method initCommonVariable() now), a CloudSimShutDown (which is derived from SimEntity) instance is created 
+			 * (with numuser as 1, its name as CloudSimShutDown, id as -1, and state as RUNNABLE). Then this new entity is added to the simulation 
+			 * While being added to the simulation, its id changes to 0 (from the earlier -1). The two collections - entities and entitiesByName are updated with this SimEntity.
+			 * the shutdownId (whose default value was -1) is 0    
+			 * Once initCommonVariable() returns (note that we are in method init() now), a CloudInformationService (which is also derived from SimEntity) instance is created 
+			 * (with its name as CloudInformatinService, id as -1, and state as RUNNABLE). Then this new entity is also added to the simulation. 
+			 * While being added to the simulation, the id of the SimEntitiy is changed to 1 (which is the next id) from its earlier value of -1. 
+			 * The two collections - entities and entitiesByName are updated with this SimEntity.
+			 * the cisId(whose default value is -1) is 1
+			 * Comment End - Dinesh Bhagwat 
+			 */
 			CloudSim.init(num_user, calendar, trace_flag);
 
 			// Second step: Create Datacenters
@@ -257,5 +270,4 @@ public class CloudSimExample1 {
 			}
 		}
 	}
-
 }
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