Converting many 'if else' statements to a cleaner approach [duplicate]

Question

My code here detects if the mimeType is equals to some MIME type, if it is, it will do a certain conversion

public void convertToMp3(File src, File target,String mimeType){     if(mimeType.equals("audio/mpeg")){         ...     }else if(mimeType.equals("audio/wav")){         mp3ToWav();     }else if(mimeType.equals("audio/ogg")){         ...     }else if(...){     ... //More if and else here } 

I have shortened my code, because it has a lot of else if statements, What design pattern is suitable for removing many if and else or else if statements?

Answer 1

You could have a Converter interface. Then you could create a class for each Mimetype like:

public interface Converter {      public void convertToMp3();     public void convertToOgg();  }  public class MpegConverter implements Converter {      public void convertToMp3() {         //Code here     }      public void convertToOgg() {         //Code here     }  } 

You would need a class like this for each converter. Then you could set up a map like this:

Map<String, Converter> mimeTypeMap = new HashMap<String, Converter>();  mimeTypeMap.put("audio/mpeg", new MpegConverter()); 

Then your convertToMp3 method becomes like this:

Converter converter = mimeTypeMap.get(mimeType); converter.convertToMp3(); 

Using this approach you could easily add different converters in the future.

All untested, probably doesn't compile, but you get the idea

Answer 2

If you use pre-JDK7, you may add an enum for all MIME types:

  public static enum MimeTypes {       MP3, WAV, OGG   }    public class Stuff {       ...       switch (MimeTypes.valueOf(mimeType)) {           case MP3: handleMP3(); break;           case WAV: handleWAV(); break;           case OGG: handleOGG(); break;       }   } 

And have a look at the Stack Overflow question Java - Convert String to enum on how to convert Strings to enums.