Enumerated Types - Introduction to Java Programming: Comprehensive Version - page 1286

I.3 Processing Enumerated Values Using
a Foreach Loop
Each enumerated type has a static method values() that returns all enumerated values for
the type in an array. For example,

Day[] days = Day.values();

You can use a regular for loop in (a) or a foreach loop in (b) to process all the values in
the array.

for ( int i = 0 ; i < days.length; i++)
System.out.println(days[i]);

for (Day day: days)
System.out.println(day);

Equivalent

(a)

(b)

I.4 Enumerated Types with Data Fields,
Constructors, and Methods
The simple enumerated types introduced in the preceding section define a type with a list of
enumerated values. You can also define an enumerate type with data fields, constructors, and
methods, as shown in Listing I.3.

L ISTING I.3

TrafficLight.java
1 public enum TrafficLight {
2 RED ( "Please stop" ), GREEN ( "Please go" ),
3 YELLOW ( "Please caution" );
4
5 private String description;

6
7

private TrafficLight(String description) {

8 this .description = description;

9 }
10
11 public String getDescription() {

12 return description;

13 }
14 }

The enumerated values are defined in lines 2-3. The value declaration must be the first
statement in the type declaration. A data field named description is declared in line 5 to
describe an enumerated value. The constructor TrafficLight is declared in lines 7-9. The
constructor is invoked whenever an enumerated value is accessed. The enumerated value's
argument is passed to the constructor, which is then assigned to description .
Listing I.4 gives a test program to use TrafficLight .

L ISTING I.4

TestTrafficLight.java
1 public class TestTrafficLight {
2 public static void main(String[] args) {
3 TrafficLight light = TrafficLight.RED;
4 System.out.println(light.getDescription());
5 }
6 }