Question

I have enum say ErrorCodes that

public enum ErrorCodes { 
       INVALID_LOGIN(100),
       INVALID_PASSWORD(101),
       SESSION_EXPIRED(102) ...;

       private int errorCode;

       private ErrorCodes(int error){
              this.errorCode = error;
       }    //setter and getter and other codes
}

now I check my exception error codes with this error codes. I don’t want to write if this do this, if this do this. How I can solve this problem (writing 10+ if blocks)

Is there any design patter to that situation ?

Thanks

Answer 1

As pointed out by Spoike, using polymorphism to pick the right error handling method is an option. This approach basically defers the 10+ if blocks to the JVM’s virtual method lookup, by defining a class hierarchy.

But before going for a full-blown class hierarchy, also consider using enum methods. This option works well if what you plan to do in each case is fairly similar.

For example, if you want to return a different error message for each ErrorCode, you can simply do this:

// Note singular name for enum
public enum ErrorCode { 
   INVALID_LOGIN(100, "Your login is invalid"),
   INVALID_PASSWORD(101, "Your password is invalid"),
   SESSION_EXPIRED(102, "Your session has expired");

   private final int code;
   private final String 

   private ErrorCode(int code, String message){
          this.code = code;
          this.message = message;
   }

   public String getMessage() {
       return message;
   }
}

Then your error handling code becomes just:

ErrorCode errorCode = getErrorCode();
prompt(errorCode.getMessage());

One drawback of this approach is that if you want to add additional cases, you’ll need to modify the enum itself, whereas with a class hierarchy you can add new cases without modifying existing code.