Use the NavigableMap ceilingEntry() method to returna key-value mapping associated with the least key greater than or equal to the given keyThe following is an example to implement ceilingEntry() method −Example Live Demoimport java.util.*; public class Demo { public static void main(String[] args) { NavigableMap n = new TreeMap(); n.put(5, "Tom"); n.put(9, "John"); n.put(14, "Jamie"); n.put(1, "Tim"); n.put(4, "Jackie"); n.put(15, "Kurt"); n.put(19, "Tiger"); n.put(24, "Jacob"); System.out.println("NavigableMap elements..."+n); System.out.println("Ceiling Entry = " + n.ceilingEntry(11)); } }OutputNavigableMap elements... {1=Tim, 4=Jackie, 5=Tom, 9=John, 14=Jamie, 15=Kurt, 19=Tiger, 24=Jacob} Ceiling Entry = 14=Jamie

The higher() method in NavigableSet returns the least element strictly greater than the given element i.e. 35 here −higher(35);The following is an example to implement the higher method in Java −Example Live Demoimport java.util.NavigableSet; import java.util.TreeSet; public class Demo { public static void main(String[] args) { NavigableSet set = new TreeSet(); set.add(10); set.add(25); set.add(40); set.add(55); set.add(70); set.add(85); set.add(100); System.out.println("Returned Value = " + set.higher(35)); } }OutputReturned Value = 40

The floor() method returns the greatest element less than or equal to the given element i.e. 30 here −floor(30)The following is an example to implement the floor method in Java −Example Live Demoimport java.util.NavigableSet; import java.util.TreeSet; public class Demo { public static void main(String[] args) { NavigableSet set = new TreeSet(); set.add(10); set.add(25); set.add(40); set.add(55); set.add(70); set.add(85); set.add(100); System.out.println("Returned Value = " + set.floor(30)); } }OutputReturned Value = 25

With Java, you can initialize a set without using add() method.For this create a string array −String arr[] = { "A", "B", "C", "D", "E"};Now, use Set and asList() method to initialize the above string array to our Set −Set s = new HashSet(Arrays.asList(arr));The following is an example to initialize a set without using add() method −Example Live Demoimport java.util.Arrays; import java.util.HashSet; import java.util.Set; public class Demo { public static void main(String[] a) { String arr[] = { "A", "B", "C", "D", "E"}; Set s = ... Read More

The NavigableMap put() method is used to set a specific key and value in the NavigableMap.The following is an example to implement NavigableMap put() method −Example Live Demoimport java.util.*; public class Demo { public static void main(String[] args) { NavigableMap n = new TreeMap(); n.put(5, "Tom"); n.put(9, "John"); n.put(14, "Jamie"); n.put(1, "Tim"); n.put(4, "Jackie"); n.put(15, "Kurt"); ... Read More

To get lower key means returning the greatest key strictly less than the given key. This can be done using lowerKey() method.The following is an example to get lower key from NavigableMap −Example Live Demoimport java.util.*; public class Demo { public static void main(String[] args) { NavigableMap n = new TreeMap(); n.put(5, "Tom"); n.put(9, "John"); n.put(14, "Jamie"); n.put(1, "Tim"); n.put(4, "Jackie"); ... Read More

Use the remove() method to remove value from HashMap.First, create a HashMap and add elements −HashMap hm = new HashMap(); hm.put("Wallet", new Integer(700)); hm.put("Belt", new Integer(600)); hm.put("Backpack", new Integer(1200));Now, remove a value, let’s say with key “Wallet” −Object ob = hm.remove("Wallet");The following is an example to remove a value from HashMap −Example Live Demoimport java.util.*; public class Demo { public static void main(String args[]) { // Create hash map HashMap hm = new HashMap(); hm.put("Wallet", new Integer(700)); ... Read More

Let us first create a HashMap and add elements −HashMap hm = new HashMap(); hm.put("Wallet", new Integer(700)); hm.put("Belt", new Integer(600));To display the content, just print the HashMap object −System.out.println("Map = "+hm);The following is an example to display content of a HashMap −Example Live Demoimport java.util.*; public class Demo { public static void main(String args[]) { // Create hash map HashMap hm = new HashMap(); hm.put("Wallet", new Integer(700)); hm.put("Belt", new Integer(600)); System.out.println("Map = "+hm); } }OutputMap = {Belt=600, Wallet=700}

Use the clear() method to remove all elements from NavigableMap in Java.First, let us create NavigableMap −NavigableMap n = new TreeMap();Add elements to the NavigableMap −n.put(5, "Tom"); n.put(9, "John"); n.put(14, "Jamie"); n.put(1, "Tim"); n.put(4, "Jackie"); n.put(15, "Kurt"); n.put(19, "Tiger"); n.put(24, "Jacob");Remove all elements −n.clear();The following is an example to remove all elements from Java NavigableMap −Example Live Demoimport java.util.*; public class Demo {    public static void main(String[] args) {       NavigableMap n = new TreeMap();       n.put(5, "Tom");       n.put(9, "John");       n.put(14, "Jamie");       n.put(1, "Tim");       ... Read More

To count the number of elements in a HashSet, use the size() method.Create HashSet −String strArr[] = { "P", "Q", "R" }; Set s = new HashSet(Arrays.asList(strArr));Let us now count the number of elements in the above Set −s.size()The following is an example to count the number of elements in a HashSet −Example 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 s = new HashSet(Arrays.asList(strArr));       System.out.println("Elements: "+s);       System.out.println("Number of Elements: ... Read More