Object

An object is an instance of a class stored in a set of memory locations.

Related concepts:  ClassTypeValue

Closest Wikipedia entry:  Object-oriented programming — Object-oriented programming (OOP) is a programming paradigm based on the concept of objects, which can contain data and code: data in the form of fields (often known as attributes or properties), and code in the form of procedures (often known as methods). In OOP, computer programs are designed by making them out of objects that interact with one another. Many of the most widely used programming languages (such as C++, Java, and Python) are multi-paradigm and support object-oriented programming to a greater or lesser degree, typically in combination with imperative programming, procedural programming and functional programming.

Misconceptions about Object

35 documented Misconceptions

AssignmentCopiesObject

Assignment copies the object

BoxedNull

Passing null to a wrapper class constructor creates an object representing the absence of a value

ChainedMethodsNotCalledFromOutside

Chained methods are all called on the object at the beginning of the chain

EqualityOperatorComparesObjectsValues

o==p compares the objects referred to by variables o and p

EqualsComparesReferences

o.equals(p) compares the references stored in the variables o and p

FrameIsClassInstance

A stack frame is the same as an instance of a class

MethodAsField

Each object contains its own special fields for all of its methods

MultiReferenceVariable

A reference variable can point to multiple objects

NestedObjectsImplyNestedClasses

If objects are part of a containment hierarchy, their classes are nested, too

NoFieldInheritance

An object contains only the fields declared in its class

NoFieldlessObjects

Objects without instance variables can't exist

NoInsideMethodCallInConstructor

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

NullIsObject

null is an object

ObjectLabeledWithConstructorSignature

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

ObjectLabeledWithVariableName

In stack and heap diagrams, an object on the heap is labeled with the name of the variable that refers to it

PrimitiveIsObject

Primitive values are heap objects

ReferenceLabeledWithDynamicType

In stack and heap diagrams, reference variables are labeled with the types of the objects they refer to

SuperclassObjectAllocated

When instantiating an object of a subclass, an object of a superclass is also allocated

ThisAsField

this is a special field in the object

ThisAssignable

One can assign to this

ThisExistsInStaticMethod

this is a local variable, also in static methods

VariablesHoldObjects

A variable of a reference type contains a whole object