Constructor

A constructor is a function that initializes a newly allocated object.

Related concepts:  ClassObjectMethod

Closest Wikipedia entry:  Constructor (object-oriented programming) — In class-based, object-oriented programming, a constructor (abbreviation: ctor) is a special type of function called to create an object. It prepares the new object for use, often accepting arguments that the constructor uses to set required member variables. A constructor resembles an instance method, but it differs from a method in that it has no explicit return type, it is not implicitly inherited and it usually has different rules for scope modifiers.

Misconceptions about Constructor

18 documented Misconceptions

AllClassesHaveDefaultConstructor — Java

All classes automatically get a no-argument constructor

CannotChainAttributeToObjectInstantiation — Python

Method calls, and attribute accesses in general, cannot be chained to a constructor invocation.

CannotChainMemberToConstructor — Java

Method calls or field accesses cannot be chained to a constructor invocation

ConstructorAllocates — Java

The constructor allocates the object

ConstructorParameterIsField — Java

Formal constructor parameters are equivalent to instance variables

ConstructorReturnsObject — Java

Constructors need to return objects

ConstructorWithoutNew — Java

One can write the constructor name, without new, to instantiate a class

ImmutableRequiresFinalParameters — Java

Immutable classes need final constructor/method parameters

InitCreates — Python

__init__ must create a new object

InitReturnsObject — Python

__init__ needs to return an object

MustInitializeFieldInConstructor — Java

Constructors must assign values to all fields

NoEmptyConstructor — Java

A constructor must do something

NoEmptyInit — Python

__init__ must do something

NoInsideMethodCallInConstructor — Java

It is foirbidden to call other methods on the same object while inside its constructor

ObjectLabeledWithConstructorSignature — Java

In stack and heap diagrams, an object on the heap is labeled like a stack frame of a constructor call

ObjectsMustBeNamed — Java

A variable is needed to instantiate an object

ObjectsMustBeNamed — Python

A variable is needed to instantiate an object

ThisInConstructorIsNull — Java

In a constructor, this is null