Java Enum Introduction

An Enumeration is a list of named constants. We can create constants in Java using final and static keywords as well. But whenever we want a variable to hold a value from a set of valid values, enumerations can be used and has advantage over constants created using final keyword.

For example,
Consider a pizza ordering application where the pizza sizes are represented as constants as follows.

public static final int SMALL = 1;
public static final int MEDIUM = 2;
public static final int LARGE = 3;

And in some part of the code, we may check some conditions like,

if(pizzaSize == SMALL)
	makeSmallPizza();
else if(pizzaSize == MEDIUM)
	makeMediumPizza();
else if(pizzaSize == LARGE)
	makeLargePizza();

where, value of pizzaSize is set in some part of code. If the ‘pizzaSize’ variable is set a value other than 1, 2 or 3 – which is possible because ‘pizzaSize’ is nothing but an int variable so we can set it to any value in integer range – the code may not go wrong as we expect. This is where enums (enumerations) come to the rescue.

Before we say how enum solves this problem of assigning bad/illegal values, we will see how to define and use an enum.