Java: How can I check an observable list in Java to make sure it contains at least one value before...












0















I am fairly new at Java, doing a class project where I need to make a user interface using Java FXML for a company inventory system and then make it workable. I have parts and products that are added, deleted, modified, etc. Each product has a variety of parts and when you modify the product you can add/delete parts. There must be at least one part in the product at all time.



I have a table that represents all of the parts in a particular product, and I need to modify it to where it will not delete a part if it's the only part in the observable list for that product.



Currently I'm using the below to delete the parts which works fine, but obviously does not stop me from fully deleting. I was thinking that using the is.Empty method might help because if it's empty, I can pop up an error saying 'you must have at least one part'. However I'm having trouble implementing that. I was also thinking a while or if/then statement could be useful, because I could just put the segment for deleting inside the while or if/then loop with the condition the observable list isn't empty and the error in the case it is, but I'm not totally sure how I would implement that either and haven't found any resources within my textbooks. I was hoping for a pointer in the right direction, or advice if I'm just completely looking at it the wrong way. 



selectedProduct.getAssociatedPart().remove(partsinproduct.getSelectionModel().getSelectedItem());





java observablelist







share|improve this question



























    0















    I am fairly new at Java, doing a class project where I need to make a user interface using Java FXML for a company inventory system and then make it workable. I have parts and products that are added, deleted, modified, etc. Each product has a variety of parts and when you modify the product you can add/delete parts. There must be at least one part in the product at all time.



    I have a table that represents all of the parts in a particular product, and I need to modify it to where it will not delete a part if it's the only part in the observable list for that product.



    Currently I'm using the below to delete the parts which works fine, but obviously does not stop me from fully deleting. I was thinking that using the is.Empty method might help because if it's empty, I can pop up an error saying 'you must have at least one part'. However I'm having trouble implementing that. I was also thinking a while or if/then statement could be useful, because I could just put the segment for deleting inside the while or if/then loop with the condition the observable list isn't empty and the error in the case it is, but I'm not totally sure how I would implement that either and haven't found any resources within my textbooks. I was hoping for a pointer in the right direction, or advice if I'm just completely looking at it the wrong way. 



    selectedProduct.getAssociatedPart().remove(partsinproduct.getSelectionModel().getSelectedItem());





    java observablelist







    share|improve this question

























      0












      0








      0








      I am fairly new at Java, doing a class project where I need to make a user interface using Java FXML for a company inventory system and then make it workable. I have parts and products that are added, deleted, modified, etc. Each product has a variety of parts and when you modify the product you can add/delete parts. There must be at least one part in the product at all time.



      I have a table that represents all of the parts in a particular product, and I need to modify it to where it will not delete a part if it's the only part in the observable list for that product.



      Currently I'm using the below to delete the parts which works fine, but obviously does not stop me from fully deleting. I was thinking that using the is.Empty method might help because if it's empty, I can pop up an error saying 'you must have at least one part'. However I'm having trouble implementing that. I was also thinking a while or if/then statement could be useful, because I could just put the segment for deleting inside the while or if/then loop with the condition the observable list isn't empty and the error in the case it is, but I'm not totally sure how I would implement that either and haven't found any resources within my textbooks. I was hoping for a pointer in the right direction, or advice if I'm just completely looking at it the wrong way. 



      selectedProduct.getAssociatedPart().remove(partsinproduct.getSelectionModel().getSelectedItem());





      java observablelist







      share|improve this question














      I am fairly new at Java, doing a class project where I need to make a user interface using Java FXML for a company inventory system and then make it workable. I have parts and products that are added, deleted, modified, etc. Each product has a variety of parts and when you modify the product you can add/delete parts. There must be at least one part in the product at all time.



      I have a table that represents all of the parts in a particular product, and I need to modify it to where it will not delete a part if it's the only part in the observable list for that product.



      Currently I'm using the below to delete the parts which works fine, but obviously does not stop me from fully deleting. I was thinking that using the is.Empty method might help because if it's empty, I can pop up an error saying 'you must have at least one part'. However I'm having trouble implementing that. I was also thinking a while or if/then statement could be useful, because I could just put the segment for deleting inside the while or if/then loop with the condition the observable list isn't empty and the error in the case it is, but I'm not totally sure how I would implement that either and haven't found any resources within my textbooks. I was hoping for a pointer in the right direction, or advice if I'm just completely looking at it the wrong way. 



      selectedProduct.getAssociatedPart().remove(partsinproduct.getSelectionModel().getSelectedItem());





      java observablelist




      java observablelist






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked Nov 15 '18 at 19:49









      CassieCassie

      11




      11
























          1 Answer
          1






          active

          oldest

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          1














          I think, a little bit simplified, the problem will look like



          list.remove(elem);



          ... but do it only, if elem is not the only element in the list.



          This is the code for doing it:



          if (list.size() > 1)
          
  list.remove(elem);


          When there is only one element in the list, you must not remove it. Without the if it would only be removed if it would match. In an empty list you cannot remove the element anyway. When there are two or more elements in the list, you are allowed to remove.






          share|improve this answer
























          • Thanks for your answer! Does list.size work for an observable list as well? I am trying to implement that using the name of my observable list or using observablelist.size but i'm getting errors in running it.

            – Cassie
            Nov 15 '18 at 21:51











          • It depends on what you want to check. I assumed that the list is an object of some class that implements the interface List. If does not depend on what is in the list. But be aware that the elements' equals() method. will be used to identifiy the element to be removed with list.remove. For the list of Observer in an Observable, use its methods countObserversand deleteObserver.

            – Donat
            Nov 15 '18 at 22:28













          • Thank you for your help! I'm going to read read up on the methods you mentioned as they aren't ones I'm super familiar with at this point and I am eager to understand them more.

            – Cassie
            Nov 15 '18 at 23:02











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          1 Answer
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          active

          oldest

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          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          1














          I think, a little bit simplified, the problem will look like



          list.remove(elem);



          ... but do it only, if elem is not the only element in the list.



          This is the code for doing it:



          if (list.size() > 1)
          
  list.remove(elem);


          When there is only one element in the list, you must not remove it. Without the if it would only be removed if it would match. In an empty list you cannot remove the element anyway. When there are two or more elements in the list, you are allowed to remove.






          share|improve this answer
























          • Thanks for your answer! Does list.size work for an observable list as well? I am trying to implement that using the name of my observable list or using observablelist.size but i'm getting errors in running it.

            – Cassie
            Nov 15 '18 at 21:51











          • It depends on what you want to check. I assumed that the list is an object of some class that implements the interface List. If does not depend on what is in the list. But be aware that the elements' equals() method. will be used to identifiy the element to be removed with list.remove. For the list of Observer in an Observable, use its methods countObserversand deleteObserver.

            – Donat
            Nov 15 '18 at 22:28













          • Thank you for your help! I'm going to read read up on the methods you mentioned as they aren't ones I'm super familiar with at this point and I am eager to understand them more.

            – Cassie
            Nov 15 '18 at 23:02
















          1














          I think, a little bit simplified, the problem will look like



          list.remove(elem);



          ... but do it only, if elem is not the only element in the list.



          This is the code for doing it:



          if (list.size() > 1)
          
  list.remove(elem);


          When there is only one element in the list, you must not remove it. Without the if it would only be removed if it would match. In an empty list you cannot remove the element anyway. When there are two or more elements in the list, you are allowed to remove.






          share|improve this answer
























          • Thanks for your answer! Does list.size work for an observable list as well? I am trying to implement that using the name of my observable list or using observablelist.size but i'm getting errors in running it.

            – Cassie
            Nov 15 '18 at 21:51











          • It depends on what you want to check. I assumed that the list is an object of some class that implements the interface List. If does not depend on what is in the list. But be aware that the elements' equals() method. will be used to identifiy the element to be removed with list.remove. For the list of Observer in an Observable, use its methods countObserversand deleteObserver.

            – Donat
            Nov 15 '18 at 22:28













          • Thank you for your help! I'm going to read read up on the methods you mentioned as they aren't ones I'm super familiar with at this point and I am eager to understand them more.

            – Cassie
            Nov 15 '18 at 23:02














          1












          1








          1







          I think, a little bit simplified, the problem will look like



          list.remove(elem);



          ... but do it only, if elem is not the only element in the list.



          This is the code for doing it:



          if (list.size() > 1)
          
  list.remove(elem);


          When there is only one element in the list, you must not remove it. Without the if it would only be removed if it would match. In an empty list you cannot remove the element anyway. When there are two or more elements in the list, you are allowed to remove.






          share|improve this answer













          I think, a little bit simplified, the problem will look like



          list.remove(elem);



          ... but do it only, if elem is not the only element in the list.



          This is the code for doing it:



          if (list.size() > 1)
          
  list.remove(elem);


          When there is only one element in the list, you must not remove it. Without the if it would only be removed if it would match. In an empty list you cannot remove the element anyway. When there are two or more elements in the list, you are allowed to remove.







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Nov 15 '18 at 20:54









          DonatDonat

          848128




          848128













          • Thanks for your answer! Does list.size work for an observable list as well? I am trying to implement that using the name of my observable list or using observablelist.size but i'm getting errors in running it.

            – Cassie
            Nov 15 '18 at 21:51











          • It depends on what you want to check. I assumed that the list is an object of some class that implements the interface List. If does not depend on what is in the list. But be aware that the elements' equals() method. will be used to identifiy the element to be removed with list.remove. For the list of Observer in an Observable, use its methods countObserversand deleteObserver.

            – Donat
            Nov 15 '18 at 22:28













          • Thank you for your help! I'm going to read read up on the methods you mentioned as they aren't ones I'm super familiar with at this point and I am eager to understand them more.

            – Cassie
            Nov 15 '18 at 23:02



















          • Thanks for your answer! Does list.size work for an observable list as well? I am trying to implement that using the name of my observable list or using observablelist.size but i'm getting errors in running it.

            – Cassie
            Nov 15 '18 at 21:51











          • It depends on what you want to check. I assumed that the list is an object of some class that implements the interface List. If does not depend on what is in the list. But be aware that the elements' equals() method. will be used to identifiy the element to be removed with list.remove. For the list of Observer in an Observable, use its methods countObserversand deleteObserver.

            – Donat
            Nov 15 '18 at 22:28













          • Thank you for your help! I'm going to read read up on the methods you mentioned as they aren't ones I'm super familiar with at this point and I am eager to understand them more.

            – Cassie
            Nov 15 '18 at 23:02

















          Thanks for your answer! Does list.size work for an observable list as well? I am trying to implement that using the name of my observable list or using observablelist.size but i'm getting errors in running it.

          – Cassie
          Nov 15 '18 at 21:51





          Thanks for your answer! Does list.size work for an observable list as well? I am trying to implement that using the name of my observable list or using observablelist.size but i'm getting errors in running it.

          – Cassie
          Nov 15 '18 at 21:51













          It depends on what you want to check. I assumed that the list is an object of some class that implements the interface List. If does not depend on what is in the list. But be aware that the elements' equals() method. will be used to identifiy the element to be removed with list.remove. For the list of Observer in an Observable, use its methods countObserversand deleteObserver.

          – Donat
          Nov 15 '18 at 22:28







          It depends on what you want to check. I assumed that the list is an object of some class that implements the interface List. If does not depend on what is in the list. But be aware that the elements' equals() method. will be used to identifiy the element to be removed with list.remove. For the list of Observer in an Observable, use its methods countObserversand deleteObserver.

          – Donat
          Nov 15 '18 at 22:28















          Thank you for your help! I'm going to read read up on the methods you mentioned as they aren't ones I'm super familiar with at this point and I am eager to understand them more.

          – Cassie
          Nov 15 '18 at 23:02





          Thank you for your help! I'm going to read read up on the methods you mentioned as they aren't ones I'm super familiar with at this point and I am eager to understand them more.

          – Cassie
          Nov 15 '18 at 23:02




















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