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In object-oriented programming, a constructor in a class is a special method (function) that can be used to create objects of the class and never has a return type. Constructors are special instance methods that are called automatically upon the creation of an object (instance of a class). They are distinguished by having the same name as the class of the object they're associated with. Its main purpose is to pre-define the object's data members and to establish the invariant of the class, failing if the invariant isn't valid. A properly written constructor will leave the object in a 'valid' state.

Java

Example

public class Example 
{ 
  //declaration of instance variable(s).
  protected int data;
  //definition of the constructor. 
  public Example()
  {
     data = 1;
  }
}

See also

• Destructor
• Object lifetime
• Initializer

References

• Bjarne Stroustrup: The C++ Programming Language, Addison-Wesley, ISBN 0-201-70073-5

• Object-oriented programming