An ArrayList can be converted into an Array using the java.util.ArrayList.toArray() method. This method takes a single parameter i.e. the array of the required type into which the ArrayList elements are stored and it returns an Array that contains all the elements of the ArrayList in the correct order.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 aList = new ArrayList();       aList.add("James");       aList.add("Harry");       aList.add("Susan");       aList.add("Emma");       ... Read More

To get the intersection of two sets, use the retainAll() method. Here are out two set −First set −HashSet set1 = new HashSet (); set1.add("Mat"); set1.add("Sat"); set1.add("Cat");Second set −HashSet set2 = new HashSet (); set2.add("Mat"); set2.add("Cat"); set2.add("Fat"); set2.add("Hat");Get the intersection −set1.retainAll(set2);The following is an example to get the intersection of two sets −Example Live Demoimport java.util.*; public class Demo {    public static void main(String args[]) {       HashSet set1 = new HashSet ();       HashSet set2 = new HashSet ();       set1.add("Mat");       set1.add("Sat");       set1.add("Cat"); ... Read More

In this article, we will learn to get the location of an element in Java. In Java, an ArrayList is used for storing and manipulating dynamic collections of elements. When working with an ArrayList, you might need to find the index (position) of a specific element. What is the indexOf()? The location of an element in an ArrayList can be obtained using the method java.util.ArrayList.indexOf(). This method returns the index of the first occurrence of the element that is specified. If the element is unavailable in the ArrayList, then this method returns -1. Syntax int index = arrayList.indexOf(element); Finding the ... Read More

Use removeAll() method to get the asymmetric difference of two sets.First set −HashSet set1 = new HashSet (); set1.add("Mat"); set1.add("Sat"); set1.add("Cat");Second set −HashSet set2 = new HashSet (); set2.add("Mat");To get the asymmetric difference −set1.removeAll(set2);The following is an example that displays how to get the asymmetric difference between two sets −Example Live Demoimport java.util.*; public class Demo {    public static void main(String args[]) {       HashSet set1 = new HashSet ();       HashSet set2 = new HashSet ();       set1.add("Mat");       set1.add("Sat");       set1.add("Cat");       ... Read More

Use the containsValue() method to check for the existence of a value. First, create a IdentityHashMap −Map m = new IdentityHashMap();Add some elements −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 check for the existence of a value −m.containsValue(100))The following is an example to implement containsValue() method −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", ... Read More

The Stack is a data structure that is used to store elements in a Last In First Out (LIFO) manner. In Java, a stack is represented by the java.util.Stack class. It provides methods to create and manipulate a stack. Get an Element of a Stack without Removing it The pop() method of the Stack class removes the element at the top of the stack and returns it. But there is no direct way to access an element without removing it. However, we can see/view the top element of a Stack in Java using the peek() method. This method returns the ... Read More

The method java.util.Stack.empty() is used to check if a stack is empty or not. This method requires no parameters. It returns true if the stack is empty and false if the stack is not empty.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("Amy");       stack.push("John");       stack.push("Mary");       System.out.println("The stack elements are: " + stack);       System.out.println("The stack is empty? " + stack.empty());     ... Read More

The isEmpty() method is used in Java to check whether a NavigableMap is empty or not.First, create a NavigableMap and add elements to it −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");Now, check whether the Map is empty or not −System.out.println("Map is empty? " + n.isEmpty());The following is an example to implement isEmpty() method and check whether the Map is empty −Example Live Demoimport java.util.*; public class Demo {    public static void main(String[] args) {       NavigableMap n = new TreeMap();       n.put(5, ... Read More

To create a Sorted Set, firstly create a Set −Set s = new HashSet();Add elements to the above set −int a[] = {77, 23, 4, 66, 99, 112, 45, 56, 39, 89}; Set s = new HashSet(); try {    for(int i = 0; i < 5; i++) {    s.add(a[i]); }After that, use TreeSet class to sort −TreeSet sorted = new TreeSet(s);Get the last element, using the last() method −System.out.println("Last element of the sorted set = "+ (Integer)sorted.last());The following is the code to get the last element from a Sorted Set in Java −Example Live Demoimport java.util.*; public class Demo ... Read More

Fetch and remove the first element in Queue using the poll() method.Create a queue −Queue q = new LinkedList();Add some elements −q.add("abc"); q.add("def"); q.add("ghi"); q.add("jkl"); q.add("mno"); q.add("pqr"); q.add("stu"); q.add("vwx");Now, remove the first element −q.poll()The following is an example to implement the poll() method −Example Live Demoimport java.util.LinkedList; import java.util.Queue; public class Demo {    public static void main(String[] args) {       Queue q = new LinkedList();       q.add("abc");       q.add("def");       q.add("ghi");       q.add("jkl");       q.add("mno");       q.add("pqr");       q.add("stu");       q.add("vwx");   ... Read More