zoukankan      html  css  js  c++  java
  • Java Enumeration

    ref: http://www.studytonight.com/java/enumerations

    Enumerations

    Enumeration was added to Java language in JDK5. Enumeration means a list is named constant. In java, enumeration

    defines a class type. An Enumeration can have constructors, methods and instance variables. It is created using

    enum keyword. Each enumeration constant is public, static and final by default.

    Even though enumeration defines a class type and have constructors, you do not instantiate an enum using new. 

    Enumeration variables are used and declared in much a same way as you do in primitive variables

    How to Define and Use an Enumeration

    enum Subject           //Enumeration defined
    {
     Java, Cpp, C, Dbms
    }


    1. Java, Cpp, C, Dbms are called enumeration constants. They are public,static, final by default

    2. variable of enumeration can be defined directly without new keyword

    Subject sub

    3. variable of enumeration type can have only enumeration constants as value

      sub = Subject.java;


    Values( ) and ValueOf( ) method

    All the enumerations has values() and valueOf() methods inthem. 

    values() :method returns an array of enum-type containing all the enumeration constants in it.

      public static enum-type[] values()

    valueOf(): method is used to return enumeration constant whose value is equal to the string passed in as argument while calling this method

      public static enum-type valueOf(String str)

    Points to remember about Enumerations

    1. Enumeration are of class type, and have all capabilities taht a java class has

    2. Enumerations can have constructors, instance variables, methods and can even implement interfaces

    3. Enumerations are not instantiated using new 

    4. All Enumerations by default inherite java.lang.Enum class

    enum Student
    {
     John(11), Bella(10), Sam(13), Viraaj(9);
     private int age;                   //age of students
     int getage { return age; }
     public Student(int age)
     {
      this.age= age;
     }
    }
    
    class EnumDemo
    {
     public static void main( String args[] )
     {
      Student S;
      System.out.println("Age of Viraaj is " +Student.Viraaj.getage()+ "years");
     }
    }

    Output :
    Age of Viraaj is 9 years






  • 相关阅读:
    mq概念
    Mac Xampp 安装redis 及 安装php-redis扩展
    rabbitmq死信队列(延迟队列)demo
    rabbitmq生产与消费测试
    RabbitMQ各方法详解
    Mac git old mode 100644 new mode 100755 mac目录权限问题
    mac安装redis
    msql创建用户并授权
    mac apache php 访问失败
    Kubernetes入门学习--在Ubuntu16.0.4安装配置Minikube
  • 原文地址:https://www.cnblogs.com/morningdew/p/5619728.html
Copyright © 2011-2022 走看看