The java.util.HashSet class is a part of the Java collection framework. It stores unique elements, which means we cannot store the same element more than once. A HashSet can contain only one null value. If we try to add duplicate elements to a HashSet object, the elements will not be added. Adding elements to HashSet in JavaThe following are the methods used to add elements to an existing HashSet object: Using add() method Using Collections.addAll() method Using add() Method The add() method of the HashSet class is used for adding ... Read More

The size() method is used in IdentityHashMap to get the size of the map i.e. the count of elements.Let us first create IdentityHashMap and add some elements −Map 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);Now, get the size −m.size()The following is an example to get the size of the IdentityHashMap using size() method −Example Live Demoimport java.util.*; public class Demo { public static void main(String[] args) { Map m = new IdentityHashMap(); m.put("1", 100); ... Read More

To get the count of NavigableMap in Java, use the size() method.Let us first create NavigableMap and add elements −NavigableMap n = new TreeMap(); n.put(5, "Tom"); n.put(9, "John"); n.put(14, "Jamie"); n.put(1, "Tim"); n.put(4, "Jackie");Now, get the count −n.size()The following is an example to implement the size() method to get the count of the NavigableMap elements −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"); ... Read More

The elements of a Collection can be appended at the end of the ArrayList using the method java.util.ArrayList.addAll(). This method takes a single parameter i.e. the Collection whose elements are added to the ArrayList.A program that demonstrates this is given as follows −Example Live Demoimport java.util.ArrayList; import java.util.Vector; public class Demo { public static void main(String[] args) { ArrayList aList = new ArrayList(); aList.add("John"); aList.add("Sally"); aList.add("Harry"); aList.add("Martha"); ... Read More

Elements can be added in the middle of an ArrayList by using the java.util.ArrayList.add() method. This method has two parameters i.e. the index at which to insert the element in the ArrayList and the element itself. If there is an element already present at the index specified by ArrayList.add() then that element and all subsequent elements shift to the right by one.A program that demonstrates this is given as follows −Example Live Demoimport java.util.ArrayList; import java.util.List; public class Demo { public static void main(String args[]) throws Exception { List aList = new ... Read More

Use the containsKey() method and check if a given key exists in the HashMap or not.Let us first create HashMap and add some elements −// Create a hash map HashMap hm = new HashMap(); // Put elements to the map hm.put("Bag", new Integer(1100)); hm.put("Sunglasses", new Integer(2000)); hm.put("Frames", new Integer(800)); hm.put("Wallet", new Integer(700)); hm.put("Belt", new Integer(600));Now, let’s say we need to check whether the key “Bag” exists or not, For that, use the containsKey() method like this −hm.containsKey("Bag")The following is an example to check if a given key exists in HashMap −Example Live Demoimport java.util.*; public class Demo { ... Read More

To get the maximum element of HashSet, use the Collections.max() method.Declare the HashSet −Set hs = new HashSet();Now let us add the elements −hs.add(29); hs.add(879); hs.add(88); hs.add(788); hs.add(456);Let us now get the maximum element −Object obj = Collections.max(hs);The following is an example to find maximum element of HashSet −Example Live Demoimport java.util.*; public class Demo { public static void main(String args[]) { // create hash set Set hs = new HashSet(); hs.add(29); hs.add(879); ... Read More

An ArrayList can be cloned using the java.util.ArrayList.clone() method. This method does not take any parameters but returns a shallow copy the specified ArrayList instance. This means that the new ArrayList created using the ArrayList.clone() method refers to the same elements as the original ArrayList but it does not duplicate the elements.A program that demonstrates this is given as follows −Example Live Demoimport java.util.ArrayList; import java.util.List; public class Demo { public static void main(String[] args) { List aList1 = new ArrayList(); aList1.add("Apple"); ... Read More

In this article, we will learn to get the size of an ArrayList in Java. In Java, an ArrayList is a resizable array implementation of the List interface. Unlike arrays, which have a fixed length, an ArrayList dynamically grows as elements are added. Using the size() Method The size of an ArrayList can be obtained by using the java.util.ArrayList.size() method as it returns the number of elements in the ArrayList i.e. the size. Syntax int size = arrayList.size(); Getting the Size of an ArrayList  Following are the steps to get the size of an ArrayList using the size() method − ... Read More

At first, create the first HashSet and add elements to it −// create hash set 1 HashSet hs1 = new HashSet(); hs1.add("G"); hs1.add("H"); hs1.add("I"); hs1.add("J"); hs1.add("K");Create the second HashSet and add elements to it −// create hash set 2 HashSet hs2 = new HashSet(); hs2.add("G"); hs2.add("H"); hs2.add("I"); hs2.add("J"); hs2.add("K");To check whether both the HashSet are equal or not, use the equals() method −hs1.equals(hs2)The following is an example to check whether two HashSet are equal −Example Live Demoimport java.util.*; public class Demo { public static void main(String args[]) { // create hash set ... Read More