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What happens when no constructor function is declared in a class - in Java?
When any constructor is deffined in your class, the java compiler create a default no argument constructor for you. This constructor only have an invocation to the super class constructor (" super( ) ").
Why constructor rather than classes in java?
Constructor is not an alternative to class. In Java, you create classes; the classes contain methods - including the constructor, which can be viewed as a special method. If you want to have a constructor, you need a class that surrounds it, so it's not one or the other.
When you go for private constructor in java?
When you do not want any other class to be able to instantiate your current class
What is a constructor and its mandatory to use constructor in a class?
A constructor is a method that is invoked when an object is created. As to being mandatory, that really depends on the programming language; in the case of Java, each class must have a constructor, however, in many cases Java will automatically provide a default constructor, so you don't really need to program it.
Why constructor in Java doesn't have any return type?
The constructor of a Java class is not an ordinary method. Its purpose is not to return any value. The purpose of the constructor is to instantiate the class which it does. Since, the purpose of a constructor is only to instantiate and initialize its class and not anything else, it does not have a return type. All it does is creates an object of that class.
Is there a sample program for constructor?
All Java programs would have a constructor... public class Test { public Test(){ ... } ..... } This is a constructor. Even if you dont code the constructor Java would automatically place a default constructor for compilation.
How many kinds of constructor in java?
Java has 2 types of constructors based on parameters passed:Default or parameter-less constructor: A constructor which does not accept any arguments.Parametrized constructor: A constructor which accepts one or more arguments.Similarly based on Access modifier also we have:Public constructor - Class can be instantiated by anyonePrivate constructor - Class cannot be instantiated by anyoneProtected constructor - Class can be instantiated only by sub classes
What is the function of this in java?
this in java is a keyword that refers to the current object of the class. It is also used in constructor overloading when you want to invoke one constructor from another within the same class.
Does java class must have public method?
no you can have a class with no public methods and even with a a private constructor public class Example { //constructor private Example(){ } }
Can you initialize an object without constructor in java?
No. if you wish to create an object that you plan on using in a java program then the answer is NO. You cannot initialize an object of a Java class without calling the constructor.
Why do you need a constructor as a class member?
A constructor is not a mandatory member that we need to code specifically for a class. While creating a class, even if we miss out coding the constructor, Java would create a default constructor all by itself. The constructor is usually the place where we initialize things that are required by the class. Hence it is a good practice to code the constructor for our class. Tip: If you do not want anyone to instantiate your class, you can declare the constructor as private. In that way no other class can instantiate your class.
What happens if a class defines constructor but not one with no argument?
Nothing Happens. Actually such a constructor is called a Default Constructor. Even if we do not write a constructor for a class, Java would automatically place a default constructor inside the class. Ex: Public class Test { public String getName(){ return "Hi"; } } Public class TestEx { public static void main(String[] args){ Test obj = new Test(); System.out.println(obj.getName()); } } Here we were able to instantiate an object of class Test even though we did not define a constructor for that class. This is because Java automatically places a default constructor for the class.
