Thinking in Java-polymorphic

In a Java object, an object can be used either as his own type or as his base type, calling this accumulation of reference an upward transformation

Package com.paragraph.one;public enum Note{middle_c,c_sharp,b_flat;}

Package Com.paragraph.one;public class Instrument {public instrument () {//TODO auto-generated constructor STUBSYSTEM.OUT.PRINTLN ("instrument");} public void Play (Note N) {System.out.println ("Instrument.play ()");}}

Package Com.paragraph.one;public class Wind extends Instrument{public wind () {//TODO auto-generated constructor Stubsyst Em.out.println ("Wind"); public void Play (Note N) {System.out.println ("Wind.play" +n);}}

Package Com.paragraph.one;public class Music {public static void tune (instrument i) {System.out.println (i); I.play ( Note.middle_c);} public static void Main (string[] args) {Wind flutewind = new Wind (); System.out.println (flutewind); tune (Flutewind);}}

The output is:

Instrument
Wind
[Email protected]
[Email protected]
Wind.playmiddle_c

Note that the method of wind is called above, not the base class.

Associating a method call with the same method body is called binding, and binding before the program executes is called early binding, and the generic C language, such as the process-oriented language, supports only early binding, which provides a late binding for the procedural language.

In addition to the static method and the final method in Java, the other methods are late-bound, so the preceding is the output wind method, but if you add the static method, it will call the play method in instrument.

Thinking in Java-polymorphic