Use the clear() method to remove all the elements from IdentityHashMap in Java.Create a IdentityHashMap and add some elementsMap m = newIdentityHashMap(); m.put("1", 100); m.put("2", 200); m.put("3", 300); m.put("4", 150); m.put("5", 110); m.put("6", 50); m.put("7", 90); m.put("8", 250); m.put("9", 350); m.put("10", 450);Now, let us remove all the elementm.clear();The following is an example to remove all elements in IdentityHashMap in JavaExample Live Demoimport java.util.*; public class Demo {    public static void main(String[] args) {       Map m = newIdentityHashMap();       m.put("1", 100);       m.put("2", 200);       m.put("3", 300);       m.put("4", 150); ... Read More

To get the first value in TreeSet, use the first() method.First, get the TreeSet and add elements to itTreeSet tSet = new TreeSet(); tSet.add("10"); tSet.add("20"); tSet.add("30"); tSet.add("40"); tSet.add("50"); tSet.add("60");Now, get the first valuetSet.first()The following is an example to get the first value in TreeSetExample Live Demoimport java.util.*; public class Demo {    public static void main(String args[]){       TreeSet tSet = new TreeSet();       tSet.add("10");       tSet.add("20");       tSet.add("30");       tSet.add("40");       tSet.add("50");       tSet.add("60");       System.out.println("TreeSet elements...");       Iterator i = tSet.iterator(); ... Read More

To get Head Set, you need to use the headset() method. This allow a user to get a set of elements in sorted order.Firstly, set the TreeSet and add elementsTreeSet tSet = new TreeSet(); tSet.add("P"); tSet.add("Q"); tSet.add("R"); tSet.add("S");Let us now get the Head SetSortedSet s = tSet.headSet("S");The following is an example to get Head Set from TreeSet in JavaExample Live Demoimport java.util.*; public class Demo {    public static void main(String args[]){       TreeSet tSet = new TreeSet();       tSet.add("P");       tSet.add("Q");       tSet.add("R");       tSet.add("S");       System.out.println("TreeSet elements..."); ... Read More

Create TreeSet and add elements to itTreeSet tSet = new TreeSet(); tSet.add("P"); tSet.add("Q"); tSet.add("R"); tSet.add("S");Now, let us traverse elements in descending orderIterator j = tSet.descendingIterator(); while(j.hasNext()) {    System.out.println(j.next()); }The following is an example to traverse TreeSet elements in descending orderExample Live Demoimport java.util.*; public class Demo {    public static void main(String args[]){       TreeSet tSet = new TreeSet();       tSet.add("P");       tSet.add("Q");       tSet.add("R");       tSet.add("S");       System.out.println("TreeSet elements...");       Iterator i = tSet.iterator();       while(i.hasNext()){          System.out.println(i.next());     ... Read More

To get the size of IdentityHashMap, use the size() method. It returns the count of elements in the IdentityHashMap.Let us first create a IdentityHashMap and add some elements to itMap m = new IdentityHashMap(); m.put("1", 100); m.put("2", 200); m.put("3", 300); m.put("4", 150); m.put("5", 110); m.put("6", 50); m.put("7", 90); m.put("8", 250); m.put("9", 350); m.put("10", 450);Now, get the sizem.size();The following is an example to get the size of the IdentityHashMapExample Live Demoimport java.util.*; public class Demo { public static void main(String[] args) { Map m = newIdentityHashMap(); m.put("1", ... Read More

To get the set of values in IdentityHashMap, use the values() method.First, set the IdentityHashMapMap m = new IdentityHashMap(); m.put("1", 100); m.put("2", 200); m.put("3", 300); m.put("4", 150); m.put("5", 110); m.put("6", 50); m.put("7", 90); m.put("8", 250); m.put("9", 350); m.put("10", 450);Now, retrieve the set of valuesm.values()The following is an example to get the set of values in IdentityHashMap using values() methodExample Live Demoimport java.util.*; public class Demo { public static void main(String[] args) { Map m = newIdentityHashMap(); m.put("1", 100); m.put("2", 200); ... Read More

To check whether a HashSet contains another, use the contains() method.Set the first HashSetString strArr[] = { "P", "Q", "R" }; Set set1 = new HashSet(Arrays.asList(strArr));Set the second HashSetString strArr = new String[] { "P", "Q"}; Set set2 = new HashSet(Arrays.asList(strArr));Check nowset1.containsAll(set2))The following is an example to check if a HashSet collection in Java contains another CollectionExample Live Demoimport java.util.Arrays; import java.util.HashSet; import java.util.Set; public class Demo { public static void main(String[] a) { String strArr[] = { "P", "Q", "R" }; Set set1 = new ... Read More

To fetch the value for a specific key, use the get() method.As a parameter, set the key you want to fetch and fetch the value.Let’s say you need to fetch value of key 3get("3")The following is an example to fetch the value for a specific key in Java IdentityHashMap −Example Live Demoimport java.util.*; public class Demo {    public static void main(String[] args) {       Map m = newIdentityHashMap();       m.put("1", 100);       m.put("2", 200);       m.put("3", 300);       m.put("4", 150);       m.put("5", 110);       m.put("6", 50); ... Read More

Use the remove() method to remove an element from IdentityHashMap.Let us create IdentityHashMap and add some elementsMap m = new IdentityHashMap(); m.put("1", 100); m.put("2", 200); m.put("3", 300); m.put("4", 150); m.put("5", 110); m.put("6", 50); m.put("7", 90); m.put("8", 250); m.put("9", 350); m.put("10", 450);Let’s say you need to remove 2 from the Map. For that, use the remove() methodm.remove("2");The following is an example to remove an element from Java IdentityHashMapExample Live Demoimport java.util.*; public class Demo {    public static void main(String[] args) {       Map m = new IdentityHashMap(); m.put("1", 100); ... Read More

Check whether a Map is empty or not using the isEmpty() method.Let us first create a IdentityHashMap and add some elements to itMap m= new IdentityHashMap(); m.put("1", 100); m.put("2", 200); m.put("3", 300); m.put("4", 150); m.put("5", 110); m.put("6", 50); m.put("7", 90); m.put("8", 250); m.put("9", 350); m.put("10", 450);Now, use the following method to check whether the Map is empty or not. Since we added some elements above, therefore the Map is not emptyn.isEmpty();Example Live Demoimport java.util.*; public class Demo {    public static void main(String[] args) {       Map m = new IdentityHashMap(); m.put("1", 100); m.put("2", 200); m.put("3", 300); m.put("4", 150); ... Read More