Common uses of Java enumeration 7

DK1.5 introduces a new type--enumeration. In Java, although it is a "small" function, but to my development has brought "big" convenience.

Usage One: Constants

Before JDK1.5, we define constants that are: publicstaticfianl ..... Now, with enumerations, you can group related constants into an enumeration type, and enumerations provide more methods than constants.

public enum Color {    RED, GREEN, BLANK, YELLOW  }  

Usage Two: Switch

The switch statement before JDK1.6 only supports int,char,enum types, and using enumerations can make our code more readable.

Enum Signal {      GREEN, YELLOW, RED  } public  class TrafficLight {      Signal color = signal.red;      public void Change () {          switch (color) {case          RED:              color = signal.green;              break;          Case YELLOW:              color = signal.red;              break;          Case GREEN:              color = signal.yellow;              Break;}}}    

Usage Three: Add a new method to the enumeration

If you intend to customize your own method, you must add a semicolon at the end of the enum instance sequence. And Java requires that an enum instance be defined first.

public enum Color ("Red", 1), Green ("green", 2), BLANK ("White", 3), Yello ("Yellow", 4);      Member variable private String name;      private int index;          Construction method Private Color (String name, int index) {this.name = name;      This.index = index; }//Common method public static String getName (int index) {for (Color c:color.values ()) {if (c              . GetIndex () = = index) {return c.name;      }} return null;      }//Get Set method public String GetName () {return name;      } public void SetName (String name) {this.name = name;      } public int GetIndex () {return index;      } public void Setindex (int index) {this.index = index; }  }

Usage Four: Methods for overriding enumerations

An example of the ToString () method overlay is given below.

public enum Color (      "Red", 1), Green ("green", 2), BLANK ("White", 3), Yello ("Yellow", 4);      Member variable      private String name;      private int index;      Construction Method      Private Color (String name, int index) {          this.name = name;          This.index = index;      }      overriding method      @Override public      String toString () {          return this.index+ "_" +this.name;      }  }  

Usage Five: Implement Interface

All enumerations are inherited from the Java.lang.Enum class. Because Java does not support multiple inheritance, enumeration objects can no longer inherit from other classes.

Public interface Behaviour {      void print ();      String getInfo ();  }  Public enum Color implements behaviour{red      ("Red", 1), Green ("green", 2), BLANK ("White", 3), Yello ("Yellow", 4);      Member variable      private String name;      private int index;      Construction Method      Private Color (String name, int index) {          this.name = name;          This.index = index;      }  Interface method      @Override public      String getInfo () {          return this.name;      }      Interface method      @Override public      void print () {          System.out.println (this.index+ ":" +this.name);      }  }  

Usage VI: Organizing enumerations using interfaces

Public interface Food {      enum Coffee implements food{          Black_coffee,decaf_coffee,latte,cappuccino      }      Enum dessert implements food{          FRUIT, CAKE, GELATO      }  }  

Usage Seven: About the use of enumeration collections

Java.util.EnumSet and Java.util.EnumMap are two enumeration collections. Enumset guarantees that the elements in the collection are not duplicated; The key in Enummap is the enum type, and value can be any type. The use of this two collection is not mentioned here, you can refer to the JDK documentation.

For the implementation details and principles of enumerations, please refer to:

Reference: "Thinkinginjava" fourth edition

http://www.iteye.com/topic/1116193

Common uses of Java enumeration 7