EnumsExample.java

import java.util.EnumSet;
import java.util.EnumMap;

enum Directions {

    // Abstract method needs to be overriden in each of the enums
    // First line of Enum should be always enum declaration. Constructor, variables declaration not allowed.
    EAST(0) {
        @Override
        public void printDirection() {
            System.out.println("EAST");
        }
    },
    WEST(180) {
        @Override
        public void printDirection() {
            System.out.println("WEST");
        }
    }, 
    NORTH(90) {
        @Override
        public void printDirection() {
            System.out.println("NORTH");
        }
    }, SOUTH(270) {
        @Override
        public void printDirection() {
            System.out.println("SOUTH");
        }
    };

    //We can also define variables like anyother class
    int angle;

    // This constructor is called for each enum initialization
    //Constructor should be private, otherwise it'll allow to initialize objects.
    private Directions(int angle) {
        this.angle = angle;
    }

    //Enums allows abstract methods
    public abstract void printDirection();

    //Also concrete methods can be defined in enum
    public int concreteMethod() {
        System.out.println("Angle of current method: " + this.angle);
        return this.angle;
    }
}

public class EnumsExample {
    public static void main(String[] args) {
        System.out.println(Directions.EAST);
        //Calling concrete method
        Directions.EAST.concreteMethod();

        //Get all the values of enum
        Directions[] directions = Directions.values();
        for (Directions direction : directions) {
            System.out.println(direction);
        }

        //Get enum object from String
        Directions direction = Directions.valueOf("NORTH");
        System.out.println(direction);

        //Get declaration index of enum
        System.out.println(Directions.WEST.ordinal());

        //Enums can be compared using both == and .equals() method
        System.out.println(Directions.WEST == Directions.valueOf("WEST"));
        System.out.println(Directions.WEST.equals(Directions.valueOf("WEST")));

        //Use of EnumSet
        EnumSet<Directions> set = EnumSet.of(Directions.NORTH, Directions.WEST);
        set.add(Directions.EAST);

        for (Directions d: set){
            System.out.println(d);
        }

        EnumMap<Directions, Integer> map = new EnumMap<>(Directions.class);
        map.put(Directions.NORTH, Directions.NORTH.concreteMethod());

        for (Directions d1: map.keySet()){
            System.out.println(d1);
        }

    }   
}