Examples of using Java enumerations

public class test {
 public static void main(String[] args) {
  WeekDay w = WeekDay.MON;
  System.out.println(w);//I'm going to call the tostring method myself
  System.out.println(w.ordinal());//Printing is enumerating the number of objects in the list
  System.out.println(WeekDay.values().length);//How many enumeration objects are there
 }
 public enum WeekDay{
  SAT,MON,TUE,WED,THU,FRI,SAT,
  private WeekDay(){
   System.out.println("11");
  }
  private WeekDay(int a){
   System.out.println("a");
  }
 }
}

First, a simple enumeration class, the WeekDay , is defined above.    

In this class sat, mon.. And so are actually objects of the weekday class

Note:

Enumeration classes also have constructors, which must be private.

The following code should be able to understand the use of enumeration types, in conjunction with the inner class to understand

public enum TrefficLamp{
  RED(30){//The red light object calls the constructor with an int parameter,
   public TrefficLamp nextLamp(){
    return GREEN;
   }
  },
  GREEN(20){
   public TrefficLamp nextLamp(){
    return YELLOW;
   }
  },
  YELLOW(2){
   public TrefficLamp nextLamp(){
    return RED;
   }
  };
  public abstract TrefficLamp nextLamp();
  private int time;
  private TrefficLamp(int time){
   this.time = time;
  };
 }