public class Main {
enum Numbers {
ONE,
TWO,
THREE
}
public static void main(String[] args) {
Numbers ample=Numbers.TWO;
System.out.println(ample);
}
}
Enum means “specifically listed” and is a short form of “enumeration”.
When it comes to Java Enums, you can also have an enum inside a class:
Example: 
public class Main {
enum Calculator {
ADD,
SUBTRACT,
MULTIPLY,
DIVIDE
}
public static void main(String[] args) {
Calculator mrx=Calculator.MULTIPLY;
System.out.println(mrx);
}
}
As a result, we will get: MULTIPLY
Example: 
public class Main {
enum Sports {
CRICKET,
FOOTBALL,
TENNIS,
HOCKEY,
RUGBY
}
public static void main(String[] args) {
Sports ample=Sports.FOOTBALL;
System.out.println(ample);
}
}
Enum in a Switch Statement
A switch statement often checks for corresponding values using enums:
Example: 
public class Main {
enum NFL_teams{
ARIZONA_CARDINALS,
ATLANTA_FALCONS,
CAROLINA_PANTHERS,
BUFFALO_BILLS
}
public static void main(String[] args) {
NFL_teams mrx=NFL_teams.ATLANTA_FALCONS;
switch (mrx){
case ARIZONA_CARDINALS:
System.out.println("The President of Arizona Cardinals is Michael Bidwill");
break;
case ATLANTA_FALCONS:
System.out.println("The President of Atlanta Falcons is Arthur Blank ");
break;
case CAROLINA_PANTHERS:
System.out.println("The President of Carolina Panthers is David Tepper");
break;
case BUFFALO_BILLS:
System.out.println("The President of Buffalo Bills is Terry Pegula");
break;
}
}
}
Output will be as follows:
Another Example: 
public class Main {
enum NASA_projects{
ARTEMIS_1,
MARS_EXPLORATION_PROGRAM,
APOLLO_PROGRAM,
PROJECT_GEMINI
}
public static void main(String[] args) {
NASA_projects ample=NASA_projects.MARS_EXPLORATION_PROGRAM;
switch (ample){
case ARTEMIS_1:
System.out.println("The Artemis 1 mission was started in 2022");
break;
case MARS_EXPLORATION_PROGRAM:
System.out.println("The Mars Exploration Program was started in 1994");
break;
case APOLLO_PROGRAM:
System.out.println("The Apollo Program was started in 1961");
break;
case PROJECT_GEMINI:
System.out.println("The Project Gemini was started in 1965");
break;
}
}
}
Here is the output:
Loop Through an Enum
An array of enum constants can be retrieved by the values()method of the enum type. Using this method, you can loop through an enum’s constants:
Example: 
public class Main {
enum MLB_teams {
CHICAGO_WHITE_SOX,
CHICAGO_CUBS,
MINNESOTA_TWINS,
PITTSBURGH_PIRATES,
CLEVELAND_GUARDIANS
}
public static void main(String[] args) {
for (MLB_teams mrx : MLB_teams.values()) {
System.out.println(mrx);
}
}
}