Type

A type is a set of values supporting a certain set of operations.

Related concepts:  ValueClass

Closest Wikipedia entry:  Type system — In computer programming, a type system is a logical system comprising a set of rules that assigns a property called a type (for example, integer, floating point, string) to every term (a word, phrase, or other set of symbols). Usually the terms are various language constructs of a computer program, such as variables, expressions, functions, or modules. A type system dictates the operations that can be performed on a term.

Misconceptions about Type

38 documented Misconceptions

ArrayElementTypeRepeats

The type of a multi-dimensional array is written as T[] T[] T[]

ArrayElementsUntyped

Elements of arrays are untyped

ArrayLengthPartOfType

The length of an array is part of its type

ArrayRankNotPartOfType

The rank of an array is not part of its type

CharNotNumeric

Char is not a numeric type

CompositeExpressionsUntyped

Expressions that consist of multiple parts have no type

ExpressionsDynamicallyTyped

One has to evaluate an expression to determine its type

IntegerDivisionToRational

Dividing two integers can produce a rational number

LargeIntegerLong

Large integer numbers have type long

MethodWithoutReturnType

A method declaration does not need to include a return type

NamedTypeParameter

To instantiate a generic type, one needs to specify type parameter names as well as types

NoCastIfSameSize

If a variable is at least as big (bit-width) as a value, then no cast is needed to a assign the value to the variable

NoFloatLiterals

There are no float literals

NoImplicitWidening

Smaller types are never automatically converted into bigger ones without an explicit cast

NoLongLiterals

There are no long literals

NumericToBooleanCoercion

Numeric types can be coerced to boolean

PrimitiveTypeParameter

Type parameters of generic types can be assigned primitive types

PrimitiveVariablesDynamicallyTyped

The type of a primitive variable depends on its value

RecursiveMethodImpliesRecursiveType

A class with a recursive method represents part of a recursive data structure

ReferenceLabeledWithDynamicType

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

ReferenceToBooleanCoercion

Every reference type can be coerced to boolean

ReferenceToIntegerConversion

One can cast between references and ints

StaticCallPolymorphic

A static method call is dispatched polymorphically at runtime based on the argument types

SubtypeCompatibleWithSupertype

A variable of a subtype can reference an object of a supertype

SupertypeIncompatibleWithSubtype

A variable of a supertype cannot reference an object of a subtype

TargetTyping

The type of a numerical expression depends on the type expected by the surrounding context

UntypedVariables

Variable declarations don't need a type

UseOfSelfTypeImpliesRecursiveType

If a class has a method that has a local variable, parameter, or return value with the class as its type, the class is a recursive type

VoidMethodNotRecursive

A method with void return type can't be recursive

VoidMethodReturnsValue

A method with void return type can return a value