In Java a class is a user defined datatype/blue print in which we declare methods and variables.public class Sample{ }Once you declare a class you need to create an object (instantiate) it. You can create an object using various ways −Using new keywordIn general, an object is created using the new keyword as −Sample obj = new Sample();ExampleIn the following Java we have a class with name sample, which has a method (display). From the main method we are instantiating the Sample class and invoking the display() method. Live Demopublic class Sample{    public void display() {       System.out.println("This ... Read More

The public static void main(String ar[]) method is the entry point of the execution in Java. When we run a .class file JVM searches for the main method and executes the contents of it line by line.You can write the main method in your program without the static modifier, the program gets compiled without compilation errors. But, at the time of execution JVM does not consider this new method (without static) as the entry point of the program.  It searches for the main method which is public, static, with return type void, and a String array as an argument.public static int main(String[] ... Read More

Java provides various access specifiers namely private, public and protected etc...The Private modifier restricts the access of members from outside the class. A class and interface cannot be public.The Public access modifier can be associated with class, method, constructor, interface, etc. public can be accessed from any other class.The protected access modifier can be associated with variables, methods, and constructors, which are declared protected in a superclass can be accessed only by the subclasses in other package or any class within the package of the protected members' class.The default access modifier does not have keyword a variable or method declared ... Read More

Static − If you declare a method, subclass, block, or a variable static it is loaded along with the class.In Java whenever we need to call an (instance) method we should instantiate the class (containing it) and call it. If we need to call a method without instantiation it should be static. Moreover, static methods are loaded into the memory along with the class.In the case of the main method, it is invoked by the JVM directly, so it is not possible to call it by instantiating its class. And, it should be loaded into the memory along with the ... Read More

A constructor is used to initialize an object when it is created. It is syntactically similar to a method. The difference is that the constructors have the same name as their class and, have no return type.There is no need to invoke constructors explicitly these are automatically invoked at the time of instantiation.Example Live Demopublic class Example {    public Example(){       System.out.println("This is the constructor of the class example");    }    public static void main(String args[]) {       Example obj = new Example();    } }OutputThis is the constructor of the class exampleFinal methodWhenever you ... Read More

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.Example Live Demopublic class Student {    public final String name;    public final int age;    public void display(){       System.out.println("Name of the Student: "+this.name); ... Read More

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 More

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 final variable later on you cannot modify or, assign values to it. Moreover, like instance variables, final variables will not be initialized with default values.Therefore, it is mandatory to initialize final variables once you declare them.Still, if you try to declare final variables without initialization that will generate a ... Read More

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 finale it cannot be extended.Extending a final classWhen we try to extend a final class that will lead to a compilation error saying “cannot inherit from final SuperClass”ExampleIn the following Java program, we have a final class with name SuperClass and we are trying to inherent it from another class (SubClass).final class SuperClass{    public void display() {       ... Read More

The “this ” keyword in Java is used as a reference to the current object, with in an instance method or a constructor. Using this you can refer the members of a class such as constructors, variables and methods.Calling a method using this keyword from a constructorYes, as mentioned we can call all the members of a class (methods, variables, and constructors) from instance methods or, constructors.ExampleIn the following Java program, the Student class contains two private variables name and age with setter methods and, a parameterized constructor which accepts these two values.From the constructor, we are invoking the setName() ... Read More