To display the first key from NavigableMap in Java, use the firstKey() method.Let us first create NavigableMap −NavigableMap n = new TreeMap(); n.put("A", 498); n.put("B", 389); n.put("C", 868); n.put("D", 988); n.put("E", 686); n.put("F", 888); n.put("G", 999); n.put("H", 444); n.put("I", 555); n.put("J", 666);Get the first key now −n.firstKey()The following is an example to get the first key from NavigableMap −Example Live Demoimport java.util.*; public class Demo { public static void main(String[] args) { NavigableMap n = new TreeMap(); n.put("A", 498); n.put("B", ... Read More

To remove the first entry of the TreeMap, use the pollFirstEntry() method.Let us first create a TreeMap and add elements −TreeMap m = new TreeMap(); m.put(1, "India"); m.put(2, "US"); m.put(3, "Australia"); m.put(4, "Netherlands"); m.put(5, "Canada");Remove the first entry now −m.pollFirstEntry()The following is an example to remove the first entry of the TreeMap.Example Live Demoimport java.util.*; public class Demo { public static void main(String args[]) { TreeMap m = new TreeMap(); m.put(1, "India"); m.put(2, "US"); ... Read More

Use the remove() method to remove a key from a TreeMap only if it is associated with a given value. Let us first create a TreeMap and add some elements −TreeMap m = new TreeMap(); m.put(1, "India"); m.put(2, "US"); m.put(3, "Australia"); m.put(4, "Netherlands"); m.put(5, "Canada");To remove a key, set the key and the associated value here. If the associate value exists, then the key will get removed −m.remove(3, "Australia")The following is an example to remove a key from a TreeMap only if it is associated with a given value −Example Live Demoimport java.util.*; public class Demo {    public static void ... Read More

Use the remove() method to remove a key from TreeMap.Let us first create a TreeMap and add some elements −TreeMap m = new TreeMap(); m.put(1, "India"); m.put(2, "US"); m.put(3, "Australia"); m.put(4, "Netherlands"); m.put(5, "Canada");Let us remove a key now. Here, we are removing key 3 now −m.remove(3)The following is an example to remove a key from TreeMap −Example Live Demoimport java.util.*; public class Demo {    public static void main(String args[]) {       TreeMap m = new TreeMap();       m.put(1, "India");       m.put(2, "US");       m.put(3, "Australia");       m.put(4, "Netherlands");   ... Read More

A TreeMap cannot contain duplicate keys. TreeMap cannot contain the null key. However, It can have null values.Let us first see how to create a TreeMap −TreeMap m = new TreeMap();Add some elements in the form of key-value pairs −m.put(1, "India"); m.put(2, "US"); m.put(3, "Australia"); m.put(4, "Netherlands"); m.put(5, "Canada");The following is an example to create a TreeMap and add key-value pairs −Example Live Demoimport java.util.*; public class Demo {    public static void main(String args[]) {       TreeMap m = new TreeMap();       m.put(1, "India");       m.put(2, "US");       m.put(3, "Australia");     ... Read More

Use the remove() method to remove a value from TreeMap.Create a TreeMap first and add some elements −TreeMap m = new TreeMap(); m.put(1, "PHP"); m.put(2, "jQuery"); m.put(3, "JavaScript"); m.put(4, "Ruby"); m.put(5, "Java"); m.put(6, "AngularJS"); m.put(7, "ExpressJS");Now, let’s say you need to remove a value with key 5. For that, use the remove() method −Object ob = m.remove(5);The following is an example to remove a value from TreeMap −Example Live Demoimport java.util.*; public class Demo {    public static void main(String args[]) {       TreeMap m = new TreeMap();       m.put(1, "PHP");       m.put(2, "jQuery");   ... Read More

Get the TreeMap size using the size() method.First, create a TreeMap and add elements to it −TreeMap m = new TreeMap(); m.put(1, "PHP"); m.put(2, "jQuery"); m.put(3, "JavaScript"); m.put(4, "Ruby"); m.put(5, "Java"); m.put(6, "AngularJS"); m.put(7, "ExpressJS");Count the number of elements in the above TreeMap or get the size using the size() method as shown below −m.size()To get the size of TreeMap, the following is the code −Example Live Demoimport java.util.*; public class Demo {    public static void main(String args[]) {       TreeMap m = new TreeMap();       m.put(1, "PHP");       m.put(2, "jQuery");       ... Read More

In this article, we will learn how to retrieve the highest key stored in a TreeMap. We will create a simple Java program that demonstrates how to create a TreeMap, add key-value pairs to it, and then use the lastKey() method to find the highest key in the map. Problem Statement Write a Java program to get the highest key stored in TreeMap. Input {1=PHP, 2=jQuery, 3=JavaScript, 4=Ruby, 5=Java, 6=AngularJS, 7=ExpressJS} Output Highest key in TreeMap: 7 Steps  The followingare the steps to get the highest key in TreeMap − First, import the classes. ... Read More

The last element of a Linked List can be retrieved using the method java.util.LinkedList.getLast() respectively. This method does not require any parameters and it returns the last element of the LinkedList.A program that demonstrates this is given as follows −Example Live Demoimport java.util.LinkedList; public class Demo {    public static void main(String[] args) {       LinkedList l = new LinkedList();       l.add("Andy");       l.add("Sara");       l.add("James");       l.add("Betty");       l.add("Bruce");       System.out.println("The last element of the Linked List is : " + l.getLast());    } }OutputThe last ... Read More

The first element can be deleted from a LinkedList by using the method java.util.LinkedList.removeFirst(). This method does not have any parameters and it returns the first element of the LinkedList.The last element can be deleted from a LinkedList by using the method java.util.LinkedList.removeLast(). This method does not have any parameters and it returns the last element of the LinkedList.A program that demonstrates this is given as follows −Example Live Demoimport java.util.LinkedList; public class Demo {    public static void main(String[] args) {       LinkedList l = new LinkedList();       l.add("Apple");       l.add("Mango");       ... Read More