[java/en] Enum Type

Short overview about enum type.

java.html.markdown

@@ -7,6 +7,7 @@ contributors:
     - ["Simon Morgan", "http://sjm.io/"]
     - ["Zachary Ferguson", "http://github.com/zfergus2"]
     - ["Cameron Schermerhorn", "http://github.com/cschermerhorn"]
+    - ["Raphael Nascimento", "http://github.com/raphaelbn"]
 filename: LearnJava.java
 ---
 
@@ -670,6 +671,68 @@ public abstract class Mammal()
         return true;
     }
 }
+
+
+// Enum Type
+//
+// An enum type is a special data type that enables for a variable to be a set of predefined constants. The        // variable must be equal to one of the values that have been predefined for it.
+// Because they are constants, the names of an enum type's fields are in uppercase letters.
+// In the Java programming language, you define an enum type by using the enum keyword. For example, you would 
+// specify a days-of-the-week enum type as:
+
+public enum Day {
+    SUNDAY, MONDAY, TUESDAY, WEDNESDAY,
+    THURSDAY, FRIDAY, SATURDAY 
+}
+
+// We can use our enum Day like that:
+
+public class EnumTest {
+    
+    // Variable Enum
+    Day day;
+    
+    public EnumTest(Day day) {
+        this.day = day;
+    }
+    
+    public void tellItLikeItIs() {
+        switch (day) {
+            case MONDAY:
+                System.out.println("Mondays are bad.");
+                break;
+                    
+            case FRIDAY:
+                System.out.println("Fridays are better.");
+                break;
+                         
+            case SATURDAY: 
+            case SUNDAY:
+                System.out.println("Weekends are best.");
+                break;
+                        
+            default:
+                System.out.println("Midweek days are so-so.");
+                break;
+        }
+    }
+    
+    public static void main(String[] args) {
+        EnumTest firstDay = new EnumTest(Day.MONDAY);
+        firstDay.tellItLikeItIs();
+        EnumTest thirdDay = new EnumTest(Day.WEDNESDAY);
+        thirdDay.tellItLikeItIs();
+    }
+}
+
+// The output is:
+// Mondays are bad.
+// Midweek days are so-so.
+
+// Enum types are much more powerful than we show above. 
+// The enum body can include methods and other fields.
+// You can se more at https://docs.oracle.com/javase/tutorial/java/javaOO/enum.html
+
 ```
 
 ## Further Reading