Java Dynamic binding

1. Dynamic binding

Associating a method call with the same method body is called a binding.

Binding is based on the type of the object at run time, called late-bound or run-time binding. In addition to the static method and final in Java

For example, the following defines a variable of shape type, which is a shape reference that, due to late binding, gives an object reference to its subclass circle, which is ultimately called the Circle.draw () method.

1  Packagecom.khlin.binding.test;2 3  Public classApp {4      Public Static voidMain (string[] args) {5Shape shape =NewCircle ();6 Shape.draw ();7     }8 }9 Ten classShape { One      Public voidDraw () { ASystem.out.println ("i m a shape ..."); -     } - } the  - classCircleextendsShape { -      Public voidDraw () { -System.out.println ("I m a circle ..."); +     } -}

Output: i m a circle ...

2. No Dynamic binding defects

any domain will be parsed by the compiler and therefore not polymorphic.

static methods are also not polymorphic.

Take a look at the following example:

1  Packagecom.khlin.binding.test;2 3  Public classApp {4      Public Static voidMain (string[] args) {5         //shape shape = new Circle ();6         //Shape.draw ();7 8Shape shape =NewTriangel ();9         /**direct access to the domain, resulting in 0, indicating that the domain cannot be dynamically bound*/TenSystem.out.println ("Shape Field[degreeofangels]:" One+shape.degreeofangels); A         /**call method, get 180, description is dynamic bound*/ -System.out.println ("Shape [Getdegreeofangels () method]:" -+shape.getdegreeofangels ()); the         /**static methods cannot be dynamically bound*/ - shape.print (); -         /**static domains also cannot be dynamically bound*/ -System.out.println ("Shape Field[lines]:" +shape.lines); +     } - } +  A classShape { at     /**the sum of internal angles*/ -      Public intDegreeofangels = 0; -  -     /**There are several sides*/ -      Public Static Final intLines = 1; -  in      Public intGetdegreeofangels () { -         returnDegreeofangels; to     } +  -      Public voidDraw () { theSystem.out.println ("i m a shape ..."); *     } $ Panax Notoginseng      Public Static voidprint () { -System.out.println ("Printing shapes ..."); the     } + } A  the classTriangelextendsShape { +     /**the sum of internal angles*/ -      Public intDegreeofangels = 180; $  $     /**There are several sides*/ -      Public Static Final intLines = 3; -  the      Public intGetdegreeofangels () { -         returnDegreeofangels;Wuyi     } the  -      Public voidDraw () { WuSystem.out.println ("i m a Triangel ..."); -     } About  $      Public Static voidprint () { -System.out.println ("Printing Triangel ..."); -     } -}

The output is:

Shape field[degreeofangels]:0
Shape [Getdegreeofangels () method]:180
Printing Shapes ...
Shape Field[lines]:1

Java Dynamic binding