Create LinkedHashSet_Learn.java

Author: tridibsamanta

Diff for: LinkedHashSet_Learn.java

@@ -0,0 +1,203 @@
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.LinkedHashSet;
+import java.util.Set;
+
+/*
+ * A set is an unordered collection of elements allowing no duplicates,
+ * i.e. all the elements in a set are unique.
+ */
+
+public class LinkedHashSet_Learn {
+
+	public static void main(String[] args) {
+
+		/*
+		 * The 'Set' interface extends 'Collection' interface and specifies the
+		 * behaviour of a collection that does not allow duplicate elements.
+		 * 
+		 * The 'LinkedHashSet' class extends the 'HashSet' class and adds no members of
+		 * its own. It maintains a linked list of the entries in the set, in the order
+		 * in which they were inserted. Thus iterating over the set elements are done as
+		 * per insertion order of elements.
+		 */
+
+		Set<Integer> demoSet = new LinkedHashSet<>();
+
+		/*
+		 * Adding elements to LinkedHashSet
+		 * 
+		 * boolean add(E obj) : Declared in the Collection interface. Adds object to the
+		 * collection. Returns true if object was added to the collection. Returns false
+		 * if obj is already a member of the collection and the collection does not
+		 * allow duplicates.
+		 * 
+		 * boolean addAll(Collection c) : Declared in the Collection interface. Adds all
+		 * the elements of c to the invoking collection. Returns true if elements were
+		 * added to the invoking collection. Otherwise, returns false.
+		 */
+
+		demoSet.add(7);
+		// demoSet = [7]
+
+		demoSet.add(5);
+		// demoSet = [7, 5]
+
+		demoSet.add(3);
+		// demoSet = [7, 5, 3]
+
+		demoSet.add(9);
+		// demoSet = [7, 5, 3, 9]
+
+		demoSet.add(5); // 5 already exists in demoSet hence not added
+		// demoSet = [7, 5, 3, 9]
+
+		if (demoSet.add(3)) // 3 already exists in demoSet hence not added
+			System.out.println("Element added to set");
+		else
+			System.out.println("Duplicate element cannot be added to set");
+
+		System.out.println("demoSet = " + demoSet); // demoSet = [7, 5, 3, 9]
+
+		Set<Integer> numsSet = new LinkedHashSet<>(Arrays.asList(4, 7, 3, 6, 8));
+		// numsSet = [3, 4, 6, 7, 8]
+
+		numsSet.addAll(Arrays.asList(5, 7, 2, 8, 1, 3)); // duplicate elements are not added
+		// numsSet = [1, 2, 3, 4, 5, 6, 7, 8]
+
+		System.out.println("numsSet = " + numsSet); // numsSet = [1, 2, 3, 4, 5, 6, 7, 8]
+
+		/*
+		 * Removing elements from LinkedHashSet
+		 * 
+		 * boolean remove(Object obj) : Declared in the Collection interface. Removes
+		 * one instance of obj from the invoking collection. Returns true if the element
+		 * was removed. Otherwise, returns false.
+		 * 
+		 * boolean removeAll(Collection c) : Declared in the Collection interface.
+		 * Removes all elements of c from the invoking collection. Returns true if
+		 * elements were removed from the invoking collection. Otherwise, returns false.
+		 * 
+		 * boolean retainAll(Collection c) : Declared in the Collection interface.
+		 * Removes all elements from the invoking collection except those in c. Returns
+		 * true if elements were removed from the invoking collection. Otherwise,
+		 * returns false.
+		 */
+
+		// demoSet = [7, 5, 3, 9]
+		demoSet.remove(7);
+		// demoSet = [5, 3, 9]
+
+		System.out.println("demoSet = " + demoSet); // demoSet = [5, 3, 9]
+
+		// numsSet = [1, 2, 3, 4, 5, 6, 7, 8]
+		numsSet.removeAll(Arrays.asList(1, 3, 5, 7));
+		// numsSet = [2, 4, 6, 8]
+
+		System.out.println("numsSet = " + numsSet); // numsSet = [2, 4, 6, 8]
+
+		// numsSet = [2, 4, 6, 8]
+		numsSet.retainAll(Arrays.asList(4, 8));
+		// numsSet = [4, 8]
+
+		System.out.println("numsSet = " + numsSet); // numsSet = [4, 8]
+
+		/*
+		 * Get the count of elements present in the LinkedHashSet
+		 * 
+		 * int size() : Declared in the Collection interface. Returns the number of
+		 * elements held in the invoking collection.
+		 */
+
+		// demoSet = [5, 3, 9]
+		int setSize = demoSet.size();
+
+		System.out.println("Size = " + setSize); // Size = 3
+
+		/*
+		 * Check if LinkedHashSet is empty or not
+		 * 
+		 * boolean isEmpty() : Declared in the Collection interface. Returns true if the
+		 * invoking collection is empty. Otherwise, returns false.
+		 */
+
+		// demoSet = [5, 3, 9]
+		if (demoSet.isEmpty())
+			System.out.println("Set is empty !");
+		else
+			System.out.println("Set is not empty !");
+
+		/*
+		 * Check if an object is present the LinkedHashSet
+		 * 
+		 * boolean contains(Object obj) : Declared in the Collection interface. Returns
+		 * true if obj is an element of the invoking collection. Otherwise, returns
+		 * false.
+		 */
+
+		int value = 9;
+
+		// demoSet = [5, 3, 9]
+		if (demoSet.contains(value))
+			System.out.println("Set contains " + value);
+		else
+			System.out.println("Set does not contain " + value);
+
+		/*
+		 * Clear the LinkedHashSet
+		 * 
+		 * void clear() : Declared in the Collection interface. Removes all elements
+		 * from the invoking collection.
+		 */
+
+		// demoSet = [5, 3, 9]
+		demoSet.clear();
+		// demoSet = []
+
+		System.out.println("demoSet = " + demoSet); // demoSet = []
+
+		/*
+		 * Construct LinkedHashSet from array
+		 */
+
+		String fruits[] = { "apple", "grape", "banana", "orange", "grape" };
+
+		LinkedHashSet<String> fruitSet = new LinkedHashSet<>();
+
+		Collections.addAll(fruitSet, fruits);
+
+		System.out.println("fruitSet = " + fruitSet); // fruitSet = [apple, grape, banana, orange]
+
+		/*
+		 * Construct array from LinkedHashSet
+		 */
+
+		String fruitArr[] = fruitSet.toArray(new String[fruitSet.size()]);
+
+		System.out.println("fruitArr = " + Arrays.toString(fruitArr)); // fruitArr = [apple, grape, banana, orange]
+
+		/*
+		 * Iterating over the contents of a LinkedHashSet
+		 * 
+		 * Iterator<E> iterator() : Declared in the Collection interface. Returns an
+		 * iterator for the invoking collection.
+		 */
+
+		Iterator itr = fruitSet.iterator();
+
+		while (itr.hasNext()) {
+			System.out.print(itr.next() + " ");
+		}
+
+		System.out.println();
+
+		// Iterate using for-each loop
+
+		for (String fruit : fruitSet) {
+			System.out.print(fruit + " ");
+		}
+
+	}
+
+}