Java Vs Groovy - Enum Demo

 Java 5 introduced enum that solve the problem with enumeration. Groovy also support that feature, as shown here.

 Enum example using Java.

enum ShirtSize {
 SMALL,MEDIUM,LARGE,EXTRALARGE
}

class ShirtImplementation {
 public void orderShirt(ShirtSize size) {
  switch(size) {
   case SMALL :
    System.out.println("The size of the shirt is small");
    break;
   case MEDIUM :
    System.out.println("The size of the shirt is medium");
    break;
   case LARGE :
    System.out.println("The size of the shirt is large");
    break;
   case EXTRALARGE :
    System.out.println("The size of the shirt is extra large");
    break;
   default : 
    System.out.println("The shirt size is not available");
    break;
    
  }
 }
}

public class EnumExample {
 public static void main(String args[]) {
  ShirtImplementation shirtImplementation = new ShirtImplementation();
  shirtImplementation.orderShirt(ShirtSize.SMALL);
  shirtImplementation.orderShirt(ShirtSize.MEDIUM);
  shirtImplementation.orderShirt(ShirtSize.LARGE);
  shirtImplementation.orderShirt(ShirtSize.EXTRALARGE);
 }
}

The output from the above code is as follows

The size of the shirt is small
The size of the shirt is medium
The size of the shirt is large
The size of the shirt is extra large

Groovier way for implementing above example

enum ShirtSize {
 SMALL,MEDIUM,LARGE,EXTRALARGE
}

def orderShirt(size) {
 switch(size) {
  case [ShirtSize.SMALL] :
   println "The size of the shirt is small"
   break;
  case [ShirtSize.MEDIUM] :
   println "The size of the shirt is medium"
   break;
  case [ShirtSize.LARGE] :
   println "The size of the shirt is large"
   break;
  case [ShirtSize.EXTRALARGE] :
   println "The size of the shirt is extra Large"
   break;
  default :
   println "The shirt size is not available"
   break;
 }
}

orderShirt(ShirtSize.MEDIUM)
orderShirt(ShirtSize.SMALL)
orderShirt(ShirtSize.LARGE)
orderShirt(ShirtSize.EXTRALARGE)

The output from the above code is as follows

The size of the shirt is medium
The size of the shirt is small
The size of the shirt is large
The size of the shirt is extra Large
The shirt size is not available

Java 5 enum allows you to define methods and constructors, The Groovy also support that features, as shown here.

enum ShirtSize {
 SMALL(36),MEDIUM(38),LARGE(40),EXTRALARGE(44)
 final int shirtSize
 ShirtSize(size) {
  shirtSize = size 
 }
 
 def printShirtDetails() {
  println "The size of ${this} is ${shirtSize} cm"
 }
}

for(shirts in ShirtSize.values()) {
 shirts.printShirtDetails()
}

The result from the above code is as follows.

The size of SMALL is 36 cm
The size of MEDIUM is 38 cm
The size of LARGE is 40 cm
The size of EXTRALARGE is 44 cm

Java enum allows you to override or redefine the method for specific values of enum. In Groovy you can't achieve this one directly, you can achieve through inject the method into instance using ExpandoMetaClass, as show here.
Java way for overriding or redefining method of enum variable.

enum WeekEndActivity {
 SATURDAY {
  public String toString() {
   return "Play" ;
  }
 },
 SUNDAY {
  public String toString() {
   return "Relax";
  }
 };
}
public class EnumDemo {
 public static void main(String args[]) {
  System.out.println("Saturday activity : " + WeekEndActivity.SATURDAY);
  System.out.println("Sunday activity : " + WeekEndActivity.SUNDAY);
 }
}

The result from the above example is shown here.

Saturday activity : Play
Sunday activity : Relax

Groovier way for implementing above example is shown here.

enum WeekEndActivity {
 SATURDAY,SUNDAY
 def activity() {
  'Relax'
 }
}

def expandoMetaClass = new ExpandoMetaClass(WeekEndActivity)
expandoMetaClass.activity = { -> 'Play'}
expandoMetaClass.initialize()
WeekEndActivity.SATURDAY.metaClass = expandoMetaClass

for(day in WeekEndActivity.values()) {
 println "${day} - ${day.activity()}"
}

The result from the above example is shown here.

SATURDAY - Play
SUNDAY - Relax