How do I return a null from a constructor?

1 Answer

  1. Make your constructor as private.
  2. Declare a public static method to initialize your constructor using the params provided. private Foo( Id baz ){ Foo foo=new Foo(); foo.entry.baz = baz; } public static Foo getInstance( Id baz){ if(baz == null){ return null; } else { Foo foo=new Foo(baz); return foo; } }

Can you return a null pointer?

A function that returns pointer values can return a null pointer when it is unable to perform its task. (A null pointer used in this way is analogous to the EOF value that functions like getchar return.) The start pointer steps over each character position in the input string.

Can I return null in C++?

It is not only legal to return NULL, i.e. void* in C/C++, but great! Very useful to indicate the absence or invalidity of the referenced object. Yes, it is totally fine to return NULL.

What happens when constructor fails C++?

The best way to signal constructor failure is therefore to throw an exception. If you don’t have the option of using exceptions, the “least bad” work-around is to put the object into a “zombie” state by setting an internal status bit so the object acts sort of like it’s dead even though it is technically still alive.

Can a constructor be null?

And if we write a constructor with arguments or no-arguments then the compiler does not create a default constructor. Note: Default constructor provides the default values to the object like 0, null, etc. depending on the type.

What is empty constructor in C++?

Answer: C++ Empty constructor necessity depends upon class design requirements. We know that C++ class constructor is called when we create an object of a class. If a class is not required to initialize its data member or does not contain data member, there is no need to write empty constructor explicitly.

Should you ever return null?

Returning null Creates More Work An ideal function, like an assistant cook, will encapsulate work and produce something useful. A function that returns a null reference achieves neither goal. Returning null is like throwing a time bomb into the software. Other code must a guard against null with if and else statements.

How do you check if a pointer is null?

Use Pointer Value as Condition to Check if Pointer Is NULL in C++ Null pointers are evaluated as false when they are used in logical expressions. Thus, we can put a given pointer in the if statement condition to check if it’s null.

How do I return a null object?

In Java, a null value can be assigned to an object reference of any type to indicate that it points to nothing. The compiler assigns null to any uninitialized static and instance members of reference type. In the absence of a constructor, the getArticles() and getName() methods will return a null reference.

How do I return a blank in C++?

Let’s see a simple example when the list is empty.

  1. #include
  2. #include
  3. using namespace std;
  4. int main()
  5. {
  6. list li;
  7. std::cout << “empty() : ” << li.empty()<
  8. return 0;

Is it OK to throw exception in constructor?

Yes, constructors are allowed to throw an exception in Java. A Constructor is a special type of a method that is used to initialize the object and it is used to create an object of a class using the new keyword, where an object is also known as an Instance of a class.

Can constructor throw exception in C++?

When throwing an exception in a constructor, the memory for the object itself has already been allocated by the time the constructor is called. So, the compiler will automatically deallocate the memory occupied by the object after the exception is thrown.