Core Java

Author: sathishmepco

Collections/src/com/cdac/collections/collectionsutils/CollectionsDemo.java

@@ -57,35 +57,50 @@ public static void main(String[] args) {
 		iList.add(40);
 		iList.add(30);
 
+		//Binary Search in List Collection
 		int index = Collections.binarySearch(iList, 190);
-		System.out.println("Binary Search index is : "+index);
+		System.out.println("Binary Search of 190 index is : "+index);
 
+		//Copy one list to another list
+		//It does not create new list
+		//It copies the values into the new list indexs
 		ArrayList<Integer> newList = new ArrayList<>();
 		newList.add(11);
 		newList.add(12);
 		newList.add(13);
 		newList.add(14);
 		newList.add(15);
-		Collections.copy(newList, iList); //newList should have the same size as src list
-		System.out.println("Copied List : "+newList);
-		
+		//newList should have minimum size as iList
+		Collections.copy(newList, iList); 
+		System.out.println("Copying the list from another list : "+newList);
+
+		//Creating Immutable Collection
 		Set<String> emptySet = Collections.emptySet();
+		List<String> emptyList = Collections.emptyList();
+		Map<String, String> emptyMap = Collections.emptyMap();
+		System.out.println("Creating immutable collection (list, set, map)");
 		System.out.println("Empty Set : "+emptySet.size());
 		//emptySet.add("Try");  //not allowed its immutable
 
+		//replacing all the elements with the new value
 		Collections.replaceAll(iList, 10, 100);
+		System.out.println("Replacing all the 10 in the list with 100 :");
 		System.out.println(iList);
 
+		//shuffling the list
 		Collections.shuffle(iList);
+		System.out.println("Shuffle the Elements in the List : ");
 		System.out.println(iList);
 
+		//Creating singleton Collection Set, List, Map
 		Set<String> singletonSet = Collections.singleton("Java");
+		System.out.println("Creating singleton Collection : ");
 		System.out.println(singletonSet);
 //		singletonSet.add("Hello"); //not supported its immutable
 
+		//Creating synchronized Collection List, Set, Map
 		Map<Integer, String> map = new HashMap<>();
 		map = Collections.synchronizedMap(map);
-		
-		
+		System.out.println("Creating synchronizing Collection : ");
 	}
-}
+}

Generics/src/com/cdac/generics/NumberDatabaseMain.java

@@ -17,7 +17,7 @@ public static void main(String[] args) {
 		longDatabase.set(1200000000L);
 		System.out.println("Long from database : "+longDatabase.get());
 
-		//NumberDatabase<String> stringDatabase = new NumberDatabase<>();
+//		NumberDatabase<String> stringDatabase = new NumberDatabase<>();
 		//the above code will throw error
 		//String class is not derived from Number class
 

Generics/src/com/cdac/generics/StringDB.java

@@ -12,6 +12,7 @@ public static void main(String[] args) {
 
 		Database<Date> date = new Database<>();
 		date.set(new Date());
+		Date dd = date.get();
 //		String abc = (String)date.get();  // not ok
 	}