Java Constructors are used to initialize an object with a default value.That is the sole purpose of Constructor in Java. Let us suppose we have a class, Person. We want to create an object of class Person.What do we do ? Person person = new Person();What if we want to create another person object and assign a name this time ? Person anotherPerson ...

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The important difference between constructors and methods are: Constructors create and initialize objects that don't exist yet, while methods perform operations on objects that already exist. Constructors can't be called directly; they are called implicitly when the new keyword creates an object. Methods can be called directly on an object that has...

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Yes.This is called constructor-overloading.Depending upon the necessity, we can call different constructors to initialize different objects of the same class. public class Person { private String name; public Person() { super(); } public Person(String name) { super(); this.name = name; } } We can call one cons...

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As we have seen earlier, a constructor must have this() to call another constructor in the same class or super() to call the constructor of the super class as the first line. Eventually the constructor of the super class must be called. The call is then propagated to the constructor of its own super-class.Thus traversing the hierarchy, ultimately t...

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A constructor that have no parameter is known as default constructor. Syntax of default constructor: (){} Lets see a simple example first: Refer the comments in the below program. class Car{ /*The following is the default constructor for this */ public Car(){ System.out.println("Default constructor"); } public voi...

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A constructor can have all sorts of access modifiers including private. However, a private constructor of a class cannot be called from its sub-class using super(…) since it will not be visible to the sub-class. If the private constructor is the only constructor of a class then the sole purpose of having that is to prevent sub-classing. Singleton c...

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In this case Java will treat this code as a normal method , It is not a constructor at all. But compiler gives a warning saying that method has a constructor name. The int TestClass()  is just a method with default scope and returning an int value. class TestClass { int TestClass() { return 0; //No Compile time error but just a w...

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Yes, We can create an object without using new operator. There are some other ways to create objects other than using new operator. But, 95% of object creation in java is done through new operator only. 1) Using newInstance() Method aka. Dynamic class Loading Class c = Class.forName("com.tuturself.TestClass"); TestClass object = (TestClass) c.ne...

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No. There is no such way in java to call sub class constructor from a super class constructor. Logically there is no way for a super class to know which are its subclasses.

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Consider the following example class Student { public void doSomeTask() { System.out.println("Doning Task!!"); } public static void main(String args[]) { Student obj = new Student(); obj.doSomeTask(); } } If you notice the code in public static void main then y...

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Unlike C++, Java doesn’t create a default copy constructor if we don’t write our own. But, Java supports copy Constructors. Copy constructor provides the facility to create an object from another object of same type received as constructor argument. There are many ways to copy the values of one object into another in java. They are: By constructor ...

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This is a most frequently asked java interview question. The answer is No, interface cannot have constructors. Now let us check by an example that why constructors in interface are not allowed in Java. Interface methods are by default public and abstract. It is the responsibility of the implementing class to define the body of the method. For e.g. ...

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Like method overloading we can overload constructors also. We can have multiple constructors in a class. Along with default constructor, we can have constructors with parameters. The no of parameters can be same, and it can have different datatypes. Below example gives sample code for constructors overloading.Following is an Example: package com....

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No, static constructors are not allowed in Java. Lets check from the example why? public class Student { /* below is a static constructor */ public static Student() { System.out.println("Static Constructor of the class"); } public static void main(String args[]) { /* Now we are trying to crea...

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Instance initializer blocks are simply a block of code {} which can be used to do execute some pre-initialization logic or just initialize certain fields before they are used. An example would be the following. class A{     int a;     double b=Math.random();     {         if (b>0.5)             a=1;         else             a=-1;     }  } The above...

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