Last day I started using Realm as Android storage rather than Sqlite.
Everything went well till I searched for some pros and cons; someone said that it doesn't support delete (I was shocked). but I found that there is a delete section in documentation and I implemented sample application that adds 150 row and then I 'delete' them as the following answer said.
The size of list after deleteing is 0 which is logically right. But when I checked the size of myDB.realm file in the 'data/data/' path in the emulator, I found it the same size of the file before deleting. So does Realm flag items as deleted or physically deleting it?