Java (enum)

Java 4 12 7

Java enum , 

enum Color 
{ 
    RED, GREEN, BLUE; 
}

Color RED, GREEN, BLUE

enum Color
{
    RED, GREEN, BLUE;
}
 
public class Test
{
    //
    public static void main(String[] args)
    {
        Color c1 = Color.RED;
        System.out.println(c1);
    }
}

RED

public class Test
{
    enum Color
    {
        RED, GREEN, BLUE;
    }
 
    //
    public static void main(String[] args)
    {
        Color c1 = Color.RED;
        System.out.println(c1);
    }
}

RED

Class public static final

Color 

class Color
{
     public static final Color RED = new Color();
     public static final Color BLUE = new Color();
     public static final Color GREEN = new Color();
}

for

enum Color
{
    RED, GREEN, BLUE;
}
public class MyClass {
  public static void main(String[] args) {
    for (Color myVar : Color.values()) {
      System.out.println(myVar);
    }
  }
}

RED
GREEN
BLUE

switch

switch

enum Color
{
    RED, GREEN, BLUE;
}
public class MyClass {
  public static void main(String[] args) {
    Color myVar = Color.BLUE;

    switch(myVar) {
      case RED:
        System.out.println("");
        break;
      case GREEN:
         System.out.println("");
        break;
      case BLUE:
        System.out.println("");
        break;
    }
  }
}


values(), ordinal()  valueOf() 


enum  java.lang.Enum  java.lang.Serializable  java.lang.Comparable 


values(), ordinal()  valueOf()  java.lang.Enum 


  • 
values() 
  • 
ordinal()
  • 
valueOf()




 

enum Color 

{ 

    RED, GREEN, BLUE; 

} 

  

public class Test 

{ 

    public static void main(String[] args) 

    { 

        //  values() 

        Color[] arr = Color.values(); 

  

        // 

        for (Color col : arr) 

        { 

            // 

            System.out.println(col + " at index " + col.ordinal()); 

        } 

  

        //  valueOf()  IllegalArgumentException 

        System.out.println(Color.valueOf("RED")); 

        // System.out.println(Color.valueOf("WHITE")); 

    } 

} 






RED at index 0
GREEN at index 1
BLUE at index 2
RED



 private 

 



 

enum Color 

{ 

    RED, GREEN, BLUE; 

  

    // 

    private Color() 

    { 

        System.out.println("Constructor called for : " + this.toString()); 

    } 

  

    public void colorInfo() 

    { 

        System.out.println("Universal Color"); 

    } 

} 

  

public class Test 

{     

    // 

    public static void main(String[] args) 

    { 

        Color c1 = Color.RED; 

        System.out.println(c1); 

        c1.colorInfo(); 

    } 

} 




Constructor called for : RED
Constructor called for : GREEN
Constructor called for : BLUE
RED
Universal Color