for each inside a for each - Java

Question

for  Tweet tweet   tweets                        for long forId   idFromArray           long tweetId   tweet getId            if forId    tweetId               String twitterString   tweet getText                db insertTwitter twitterString  tweetId                       My code won t run pass the first for   loop  that s why idFromArray is empty since I don t add anything there until a tweet is has been added to the database   And even if there is something in the array it loops the whole thing twice  DUH  Since I have two loops  which makes the database very bloated with the same tweets   It is not a simple compare of the two tweets id and simply ignore the ones with the same id   I m pretty certain there is a really simple solution to this problem  but I still can t wrap my head around it  Anybody   UPDATE   What I want is the code to ignore the the tweetId that already is in the database  And just insert the tweets that is not in the database   I don t think I should have two for-loops  I think the second loop should be replaced with something   or maybe I m wrong

User · Accepted Answer

If I understand correctly  what you want to do  in pseudo-code is the following   for  Tweet tweet   tweets        if   db containsTweet tweet getId               db insertTweet tweet getText    tweet getId               I assume your db class actually uses an sqlite database as a backend  What you could do is implement containsTweet directly and just query the database each time  but that seems less than perfect  The easiest solution if we go by your base code is to just keep a Set around that indexes the tweets  Since I can t be sure what the equals   method of Tweet looks like  I ll just store the identifiers in there  Then you get   Set lt Integer gt  tweetIds   new HashSet lt Integer gt        or long  whatever for  Tweet tweet   tweets        if   tweetIds contains tweet getId               db insertTweet tweet getText    tweet getId             tweetIds add tweet getId               It would probably be better to save a tiny bit of this work  by sorting the list of tweets to begin with and then just filtering out duplicate tweets  You could use      if tweets is a List Collections sort tweets  new Comparator         public int compare  Object t1  Object t2               might be the wrong way around         return   Tweet t1  getId   -   Tweet t2  getId              Then process it  Integer oldId  for  Tweet tweet   tweets        if  oldId    null    oldId    tweet getId              db insertTweet tweet getText    tweet getId               oldId   tweet getId        Yes  you could do this using a second for-loop  but you ll run into performance problems much more quickly than with this approach  although what we re doing here is trading time for memory performance  of course

User · Answer

So you really want   for each tweet     unless tweet is in db         insert tweet   If so  just write it down in your programming language  Hint  The loop over the array is to be done before the insert  which is done depending on the outcome    What you want to test is that all array elements are not equal to the current one  But your for loop does not do that

User · Answer

for  Tweet   tweets         should really be  for Tweet tweet  tweets

User · Answer

Your syntax is not correct  It should be like that   for  Tweet tweet   tweets                      for long forId   idFromArray           long tweetId   tweet getId            if forId    tweetId               String twitterString   tweet getText                db insertTwitter twitterString                       EDIT  This answer no longer really answers the question since it was updated

User · Answer

most simple solution would be to set a boolean var  if to true where you do the insert statement and then in the outter loop check this and insert the tweet there if the boolean is true

[java] for each inside a for each - Java

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