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Programming Articles
Page 1530 of 2547
Set vs HashSet vs TreeSet in Java
A Set is a generic set of values with no duplicate elements. A TreeSet is a set where the elements are sorted.A HashSet is a set where the elements are not sorted or ordered. It is faster than a TreeSet. The HashSet is an implementation of a Set.Set is a parent interface of all set classes like TreeSet, HashSet, etc.Exampleimport java.util.*; public class Demo { public static void main(String args[]) { int a[] = {77, 23, 4, 66, 99, 112, 45, 56, 39, 89}; Set s = new HashSet(); try ...
Read MoreGet first entry from NavigableMap in Java
To display first entry from NavigableMap in Java, use the firstEntry() 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 entry now −n.firstEntry()The following is an example to get first entry from NavigableMap.Exampleimport java.util.*; public class Demo { public static void main(String[] args) { NavigableMap n = new TreeMap(); n.put("A", 498); n.put("B", 389); ...
Read MoreHow many ways are there to initialize a final variable in java?
In Java, final is the access modifier which can be used with a filed, class and a method.When a method if final it cannot be overridden.When a variable is final its value cannot be modified further.When a class is final it cannot be extended.Initializing a final variableOnce you declare a final variable, it is a must to initialize it. You can initialize the final instance variable −At the time of declaration as.public final String name = "Raju"; public final int age = 20;Within an instance (non-static) block.{ this.name = "Raju"; this.age = 20; }Within a default constructor.public final ...
Read MoreCheck two HashMap for equality in Java
To check whether two HashMap are equal or not, use the equals() method.Let us first create the first HashMap −// Create hash map 1 HashMap hm1 = new HashMap(); hm1.put("Shirts", new Integer(700)); hm1.put("Trousers", new Integer(600)); hm1.put("Jeans", new Integer(1200)); hm1.put("Android TV", new Integer(450)); hm1.put("Air Purifiers", new Integer(300)); hm1.put("Food Processors", new Integer(950));Let us now create the second HashMap −HashMap hm2 = new HashMap(); hm2.put("Shirts", new Integer(700)); hm2.put("Trousers", new Integer(600)); hm2.put("Jeans", new Integer(1200)); hm2.put("Android TV", new Integer(450)); hm2.put("Air Purifiers", new Integer(300)); hm2.put("Food Processors", new Integer(950));To check whether both the HashMap are equal or not, use the equals() method like this −hm1.equals(hm2)The following is ...
Read MoreHow to extend Interfaces in Java
An interface contains variables and methods like a class but the methods in an interface are abstract by default unlike a class. An interface extends another interface like a class implements an interface in interface inheritance.A program that demonstrates extending interfaces in Java is given as follows:Exampleinterface A { void funcA(); } interface B extends A { void funcB(); } class C implements B { public void funcA() { System.out.println("This is funcA"); } public void funcB() { System.out.println("This is funcB"); } } public class Demo { public ...
Read MoreByteBuffer asShortBuffer() method in Java
A view of the ByteBuffer can be created as a ShortBuffer using the asShortBuffer() method in the class java.nio.ByteBuffer. This method requires no parameters and it returns a short buffer as required. This buffer reflects the changes made to the original buffer and vice versa.A program that demonstrates this is given as follows −Exampleimport java.nio.*; import java.util.*; public class Demo { public static void main(String[] args) { int n = 50; try { ByteBuffer bufferB = ByteBuffer.allocate(n); ShortBuffer bufferS = bufferB.asShortBuffer(); ...
Read MoreThe addIfAbsent() method of CopyOnWriteArrayList in Java
The addIfAbsent() method appends the element if it is not in the list. If the element is already in the list, then FALSE is returned.The syntax is as follows.public boolean addIfAbsent(E ele)Here, ele is the element to be added to this list, if it is not already in the list.To work with CopyOnWriteArrayList class, you need to import the following package.import java.util.concurrent.CopyOnWriteArrayList;The following is an example to implement CopyOnWriteArrayList class addIfAbsent() method in Java.Exampleimport java.util.concurrent.CopyOnWriteArrayList; public class Demo { public static void main(String[] args) { CopyOnWriteArrayList arrList = new CopyOnWriteArrayList(); arrList.add(30); arrList.add(40); arrList.add(60); ...
Read MoreWhy final variable doesn't require initialization in main method in java?
In Java final is the access modifier which can be used with a filed class and a method.When a method if final it cannot be overridden.When a variable is final its value cannot be modified further.When a class is final it cannot be extended.Declaring final variable without initializationIf you declare a variable as final, it is mandatory to initialize it before the end of the constructor. If you don’t, a compile-time error is generated.Examplepublic class Student { public final String name; public final int age; public void display(){ System.out.println("Name of the Student: "+this.name); ...
Read MoreCreate a Stack and Queue using ArrayDeque in Java
Create a stack using ArrayDeque.Deque s = new ArrayDeque(); // stack s.push("Bat"); s.push("Mat"); s.push("Cat"); s.push("Rat"); s.push("Hat"); s.push("Fat");Create a queue using ArrayDeque −Deque q = new ArrayDeque(); // queue q.add("Bat"); q.add("Mat"); q.add("Cat"); q.add("Rat"); q.add("Hat"); q.add("Fat");The following is an example.Exampleimport java.util.ArrayDeque; import java.util.Deque; public class Demo { public static void main(String args[]) { Deque s = new ArrayDeque(); Deque q = new ArrayDeque(); // stack s.push("Bat"); s.push("Mat"); s.push("Cat"); s.push("Rat"); s.push("Hat"); s.push("Fat"); ...
Read MoreByteBuffer compact() method in Java
The buffer can be compacted using the compact() method in the class java.nio.ByteBuffer. This method does not require a parameter and it returns the new compacted ByteBuffer with the same content as the original buffer. If the buffer is read-only, then the ReadOnlyBufferException is thrown.A program that demonstrates this is given as follows −Exampleimport java.nio.*; import java.util.*; public class Demo { public static void main(String[] args) { int n = 5; try { ByteBuffer buffer = ...
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