Seven common usage summaries of Java enumerations (must see) _java

Usage One: Constants

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

Java code

public enum Color {

RED, GREEN, BLANK, Yellow

}

Usage Two: Switch

The switch statement before JDK1.6 only supports the Int,char,enum type, and using enumerations makes our code more readable.

Java code

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 sequence of enum instances. and Java requirements must first define an instance of an enum.

Java code

The public enum Color {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;

}

Normal method public

static String getName (int index) {for

(Color c:color.values ()) {

if (c.getindex () = = Inde x) {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 of overriding enumerations

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

Java code

The public enum Color {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;

}

Override method

@Override public

String toString () {return

this.index+ "_" +this.name

}

}

Usage Five: Implement Interface

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

Java code

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 Six: Organize enumerations using interfaces

Java code

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 enumerated collections. Enumset guarantees that the elements in the collection are not duplicates; The key in Enummap is the enum type, and value can be any type. The use of this two collection is not here to repeat, you can refer to the JDK documentation.

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