Question

I need small help. I have 2 lists( say A and B) which have objects of a user defined class.

Both A and B have a method getId() which would return an integer (ID). Now, I need to compare the ID of every object in List A with each and every object of List B. If the ID is same then I have to replace that object from B with that of A.

If the id of the object from A is not in B then I would add that object to B

Please provide me a logic on how to achive this

Thanks

Answer 1

Something like this would work, assuming your list is an arrayList with the possibility to access elements with an index

for(int i=0;i<a.size();i++)
    for(int j=0;j<b.size();j++)
       if(a.get(i).getId().equals(b.get(j).getId()){
         //this id from A exists in B. Replace
         b.get(j)=a.get(i);
       }
       else{
          if(j=(b.size()+1)){ // if true the whole b list have been searched
             //object not found. Add it to b
             b.add(a.get(i));      
          } 
}

This requiers that your elements in a and b override the equals statment, so they can compare the ID with eachother