Enumsal Bişiler (Note : Just For Self-reference)

1 - Enumsal bişiler

- Tanımlama:

public enum UserStatus {
    PENDING,
    ACTIVE,
    INACTIVE,
    DELETED;
}

- Kullanım:
  UserStatus.PENDING

2 - Enum & Instance

- Tanımlama:

  public enum UserStatus {
    PENDING(0,"User is pending"),
    ACTIVE(1,"User is active"),
    INACTIVE(2,"User is inactive"),
    DELETED(3,"User is deleted");

    private String message;
    priavte int index;
    
    UserStatus(String message, int index){
      this.message = message;
      this.index = index;
    }
    
    public String message(){
      return this.message;
    }
    
    public int index(){
      return this.index;
    }
 
}

- Kullanım:
  UserStatus.PENDING.message()

3 - Enum & method() - logic

public enum Operation {
    PLUS,
    MINUS,
    TIMES,
    DIVIDE;

    double calculate(double x, double y) {
        switch (this) {
            case PLUS:
                return x + y;
            case MINUS:
                return x - y;
            case TIMES:
                return x * y;
            case DIVIDE:
                return x / y;
            default:
                throw new AssertionError("Unknown operations " + this);
        }
    }

}


- Kullanımı:
    double result = Operation.PLUS.calculate(1, 2);
    System.out.println(result); //3.0

4 - Iterate Enum

public enum UserStatus {
    PENDING,
    ACTIVE,
    INACTIVE,
    DELETED;
}

for (UserStatus status : UserStatus.values()) {
    System.out.println(status);
}

- OUTPUT:
  PENDING
  ACTIVE
  INACTIVE
  DELETED

5 - Compare Enum ( == or Switch)

UserStatus status = UserStatus.PENDING;

if(status == UserStatus.PENDING) {
  System.out.println("Now : " + status.message());
}

------

switch(status){
  case PENDING:
    //...
  break;
}

6 - String To Enum or Vice Versa

- String To Enum

    Operation op = Operation.valueOf("times".toUpperCase());
    System.out.println(op.calculate(10, 3));

- Enum To String 
   
   String operationStr = Operation.TIMES.name(); //TIMES
   int order = Operation.TIMES.ordinal(); //2