Found 9326 Articles for Object Oriented Programming

Elements can be added at the beginning of a LinkedList by using the method java.util.LinkedList.addFirst(). This method has a single argument i.e. the element that is to be added at the beginning of the LinkedList.Elements can be added at the end of a LinkedList by using the method java.util.LinkedList.addLast(). This method has a single argument i.e. the element that is to be added at the end 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();   ... Read More

Use the firstKey() method to get the lowest key stored in TreeMap.Let us first set the TreeMap and add some 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");Now get the lowest key −m.firstKey()The following is an example to get the lowest key in 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");       m.put(3, "JavaScript");       m.put(4, "Ruby"); ... Read More

Use the headMap() method in Java to get ahead map. It returns a view of the portion of this map whose keys are less than or equal to.Let’s say you need to get the portion of the map above the set map (and not inclusive of it). For that, use the headMap() method like this −m.headMap(4)If you want the value 4 to be included as well, then set it as true −m.headMap(4, true)The following is an example to get Head Map from Java TreeMap −Example Live Demoimport java.util.*; public class Demo {    public static void main(String args[]) {     ... Read More

To check if a particular value exists in TreeMap, use the containsValue() method.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 we need to check that value “Java” exists or not. For that, use the containsValue() method like this −m.containsValue("Java")The following is an example to check if a particular value exists in TreeMap −Example Live Demoimport java.util.*; public class Demo {    public static void main(String args[]) {       TreeMap m = new TreeMap();       m.put(1, "PHP"); ... Read More

To check if a particular key exists in TreeMap, use the containsKey() method.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 we need to check that key 5 exists or not. For that, set the containsKey() method like this −m.containsKey(5)The following is an example to check if a particular key exists in TreeMap −Example Live Demoimport java.util.*; public class Demo {    public static void main(String args[]) {       TreeMap m = new TreeMap();       m.put(1, "PHP"); ... Read More

Let us create TreeMap in Java. It stores unique elements in ascending order −TreeMap m = new TreeMap();Now let us add some elements −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");The following is an example to create a 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");       m.put(3, "JavaScript");       m.put(4, "Ruby");       m.put(5, "Java");       m.put(6, "AngularJS");       ... Read More

To fetch LinkedHashSet key-value pair in Java, use the entrySet() method.Let us first create LinkedHashSet and add some elements −LinkedHashMap l = new LinkedHashMap(); l.put("1", "Jack"); l.put("2", "Tom"); l.put("3", "Jimmy"); l.put("4", "Morgan"); l.put("5", "Tim"); l.put("6", "Brad");Now, fetch a key-value pair −l.entrySet()The following is an example to fetch key-value pair from LinkedHashSet −Example Live Demoimport java.util.*; public class Demo {    public static void main(String[] args) {       LinkedHashMap l = new LinkedHashMap();       l.put("1", "Jack");       l.put("2", "Tom");       l.put("3", "Jimmy");       l.put("4", "Morgan");       l.put("5", "Tim");     ... Read More

Use the clone() method to copy all elements from one set to another.First HashSet −HashSet set = new HashSet (); set.add("One"); set.add("Two");Create another set and clone first set into the second −HashSet newSet = new HashSet ();Copy (clone) all elements to the second set −newSet = (HashSet)set.clone();The following is an example to copy all elements from one set to another −Example Live Demoimport java.util.*; public class Demo {    public static void main(String args[]) {       HashSet set = new HashSet ();       HashSet newSet = new HashSet ();       set.add("One"); ... Read More

First, create a Set and add elements −Set s = new HashSet(); s.add("P"); s.add(new Date()); s.add(new Long(898999)); s.add("Q"); s.add("R"); s.add(new Integer(1));Convert the above Set to a List −List l = new ArrayList(s);The following is an example to convert a set into a list in Java −Example Live Demoimport java.util.ArrayList; import java.util.Date; import java.util.List; import java.util.Set; import java.util.HashSet; public class Demo {    public static void main(String[] args) {       Set s = new HashSet();       s.add("P");;       s.add(new Date());       s.add(new Long(898999));       s.add("Q");       s.add("R");       ... Read More

The method java.util.Stack.search() is used to find if an element is in the stack or not in Java. This method takes a single parameter i.e. the element that is searched in the stack. It returns the position of the element in the stack(counting from one) if it is available and returns -1 if the element is not available in the stack.A program that demonstrates this is given as follows −Example Live Demoimport java.util.Stack; public class Demo {    public static void main (String args[]) {       Stack stack = new Stack();       stack.push("Apple");       stack.push("Mango"); ... Read More