检查我的值是否存在于数据库中？

Question

I read some data from server and save them into database . I want to check if there is any new data or not , so i request to server and get 10 post (my post have id,title, image,..) .Now I want to compare my 10 new post title that exit in my whole database . I do like this: I make ArrayList() to get data from server and to it :

   List<Post> check = new ArrayList<Post>();   

and this is my database value

   List<dbSample> txtsSave = new ArrayList<>();

and now check like this . (I check the title together ) .

         if (database.exists()) {
        for (int i = 0; i < check.size(); i++) {
            for (int j = 0; j < txtsSave.size(); j++) {
                if (check.get(i).getTitle().equals(txtsSave.get(j).getTitle())) {
                  Log.i("NewData","No new Data");
                } else {
                    Log.i("NewData"," new Data");
                }
            }
        }
    }

but I can see both Log in locat .How I can compare these together? For example my txtsave size is 30 and my check size is 10 . any suggestion?

Answer 1

do like this:

for (int i = 0; i < check.size(); i++) {
            for (int j = 0; j < txtsSave.size(); j++) {
                if (check.get(i).getTitle().equals(txtsSave.get(j).getTitle())) {
                  Log.i("NewData","No new Data");
                  break;
                } 
                if(j == (txtsSave.size() - 1))  {
                    Log.i("NewData"," new Data");
                }
            }
        }

Answer 2

I think the best way for you is to use .contains(object) in list like this:

 for (int i = 0; i < check.size(); i++) {
      if(txtsSave.contains(check.get(i)){
                Log.i("NewData","No new Data");
                txtsSave.add(check.get(i));
            } else {
                Log.i("NewData"," new Data");
            }  
  }

Answer 3

you can check check if a object exist in database by:

    public boolean hasObject(String string) {
    String selectString = "SELECT * FROM " + MY_TABLE_NAME + " WHERE column_name=?";

    Cursor cursor = myDatabase.rawQuery(selectString, new String[]{string});

    boolean hasObject = false;
    if (cursor.moveToFirst()) {
      hasObject = true;

    }

    cursor.close();    
    return hasObject;
  }