Enum

If we want to represent a Group Named Constants then we should go for enum

Example of Enum

enum Month{
JAN,FEB,MAR;
}

• Semicolon (;) is optional
• enum concept was introduced in 1.5 Version
• The main objective of enum is to Define our own Data Types(Enumerated Data Types)
• When compared with other languages enum, java enum is more powerful

Internally Implementation of enum :

• Every enum Internally implemented by using Class Concept.
• Every enum Constant is Always public static final.
• Every enum Constant Represents an Object of the Type enum.

Example of enum :

enum Month{
JAN,FEB,MAR;
}

Internal Implementation of enum

class Month{
public static final Month JAN = new Month();
public static final Month FEB = new Month();
public static final Month MAR = new Month();
}

A Tree structure using enum

package com.enumTest;

import java.util.ArrayList;
import java.util.EnumSet;
import java.util.List;

public class Demo {
	enum Month{
		JAN(1,"january",Climate.WINTER),FEB(2,"Februrary",Climate.WINTER),MAR(3,"March",Climate.SUMMER),APR(4,"April",Climate.SUMMER),
		MAY(5,"May",Climate.SUMMER),JUN(6,"June",Climate.RAINY),JUL(7,"July",Climate.RAINY),AUG(8,"August",Climate.RAINY),SEP(9,"September",Climate.RAINY),
		OCT(10,"October",Climate.WINTER),NOV(11,"November",Climate.WINTER),DEC(12,"December",Climate.WINTER);
		int width;
		String name;
		Climate climate;
		Month(int width,String name, Climate climate ){
			this.width=width;
			this.name=name;
			this.climate=climate;
		}
		public int getWidth() {
			return width;
		}
		public void setWidth(int width) {
			this.width = width;
		}
		public String getName() {
			return name;
		}
		public void setName(String name) {
			this.name = name;
		}
		public Climate getClimate() {
			return climate;
		}
		enum Climate{
			SUMMER,WINTER,RAINY;
			int totalWidth;
			public int getTotalWidth() {
				return totalWidth;
			}
			enum Decade{
				Decade;
			}
		}
	} 
	public static void main(String[] args) {
		int grandTotal;
		List<Month> temp =  new ArrayList<>();
		temp.add(Month.JAN);
		temp.add(Month.FEB);
		temp.add(Month.MAR);
		temp.add(Month.APR);
		temp.forEach(month -> month.climate.totalWidth=month.climate.totalWidth+month.width);
		EnumSet.allOf(Month.Climate.class).forEach(climate -> System.out.println(climate.totalWidth));
		grandTotal = temp.stream().mapToInt(Month::getWidth).sum();
		
		
	}
}