Java Collections

Author: smartherd

Diff for: .idea/workspace.xml

@@ -0,0 +1,55 @@
+
+import java.util.HashSet;
+import java.util.Set;
+import java.util.TreeSet;
+
+public class Main {
+
+	public static void main(String[] args) {
+
+		// Set demonstration using HashSet
+
+		Set<Integer> hashSet = new HashSet<>();
+		hashSet.add(23);
+		hashSet.add(4);
+		hashSet.add(4);
+		hashSet.add(4);
+		hashSet.add(10);
+
+		for (int element: hashSet) {
+			System.out.println(element + " ");
+		}
+
+//		hashSet.isEmpty();      // returns true, if Set is empty
+//		hashSet.contains(10);   // returns true, if the element is found
+//		hashSet.remove(23);  // returns true, if the element was deleted
+//		hashSet.clear();        // Deletes all element
+
+		System.out.println();
+
+		Set<Integer> treeSet = new TreeSet<>();
+		treeSet.add(23);
+		treeSet.add(4);
+		treeSet.add(4);
+		treeSet.add(4);
+		treeSet.add(10);
+		treeSet.add(1);
+
+		for (int element: treeSet) {
+			System.out.println(element + " ");
+		}
+	}
+}
+
+/*
+ *  Set: Interface
+ *  HashSet: Implementation
+ *  TreeSet: Implementation [sorted]
+ *
+ *  Properties:
+ *      1. Unordered Collection
+ *      2. Cannot store duplicate elements
+ *      3. It has more implementation such as HashSet, TreeHashSet and TreeSet
+ *
+ *      TreeSet contains elements in Sorted Order
+ * */

Diff for: src/23_Set_HashSet.java

@@ -0,0 +1,51 @@
+
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class Main {
+
+	public static void main(String[] args) {
+
+		/*      KEY   : VALUE
+
+		 *   "red"    : "apple"
+		 *   "yellow" : "banana"
+		 *   "white"  : "radish"
+		 *   "green"  : "apple"
+		 * */
+
+		Map<String, String> fruits = new HashMap<>();
+		fruits.put("red", "apple");
+		fruits.put("yellow", "banana");
+		fruits.put("white", "radish");
+		fruits.put("green", "apple");
+
+//		fruits.containsKey("red");      // returns true, if key is found
+//		fruits.containsValue("apple");  // returns true, if value is found
+//		fruits.size();                  // returns the size of the MAP
+//		fruits.remove("red");      // Deletes the Entry whose key is "red"
+//		fruits.clear();
+
+		System.out.println(fruits.get("red"));
+
+		for (Map.Entry pairEntry: fruits.entrySet()) {
+			System.out.println(pairEntry.getKey() + " : " + pairEntry.getValue());
+		}
+	}
+}
+
+/*
+ *   Map: Interface
+ *   HashMap: Class that implements interface Map
+ *
+ *       class HashMap implements Map {
+ *           ...
+ *       }
+ *
+ *   Map Properties:
+ *       1. They contain values based on key
+ *       2. They are not ordered
+ *       3. "KEY" should be unique
+ *       4. "VALUE" can be duplicate
+ * */