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Should every class have a default constructor?
SO, it’s upto you to design constructors. Sometimes you want user of that class to create object only by specifying values for data members (rather than having some default value ) by excluding default constructor for that class. Yes, you need to have a default constructor. The program won’t compile otherwise.
Do all classes need constructors?
All classes have constructors by default: if you do not create a class constructor yourself, Java creates one for you. However, then you are not able to set initial values for object attributes.
Is constructor compulsory?
Java doesn’t require a constructor when we create a class. However, it’s important to know what happens under the hood when no constructors are explicitly defined. The compiler automatically provides a public no-argument constructor for any class without constructors. This is called the default constructor.
When does a class have a default constructor?
A default constructor is automatically generated by the compiler if you do not explicitly define at least one constructor in your class. You’ve defined two, so your class does not have a default constructor.
When to use the Super class constructor in Java?
When extending a class, the default superclass constructor is automatically added. If you’ve overloaded your super class constructor, however, this takes the place of the default and invoking super () will thus cause a compile error as it is no longer available.
Which is the default constructor for no args?
A no-args constructor is any constructor with no arguments. A default constructor is the specific no-args constructor that is generated if no constructors are declared in a class. – Stephen C May 19 ’17 at 13:19. I didn’t say default constructor == no-args constructor but said also called .
When to use a constructor in stlcontainer?
Many constructors of STLcontainer relies on the fact that your type has a default constructor. For example for the value of an ordered associative container such as std::map. If all the members of the class have a default constructor, the compiler will implicitly generate one for your class.