java - Get a ArrayList containing the union of two different sized arraylist of some object type -

i have bean class containing 2 variables title , id.

public class bean(){     private string title;     private string id; } 

i have 2 arraylists of type bean - arraylist firstlist , arraylist secondlist. both have different number of bean elements in them i.e. size 2 arraylist different , can huge in size. of bean elements present in them may contain same ids.

now have different bean class mainbean containing 3 variables

public class mainbean(){     private string firsttitle;     private string secondtitle;     private string id; } 

i need create new arraylist of type mainbean based on values above 2 arraylist - arraylist finallist.

while comparing above 2 arraylist (firstlist , secondlist), following needs kept in mind -

1) first condition - if same id present in both lists, new arraylist finallist have id populated , firsttitle firstlist , secondtitle secondlist.

2) if id firstlist not present in secondlist, finallist have id , firsttitle firstlist while secondtitle null.

3) if id secondlist not present in firstlist, finallist have id , secondtitle secondlist while firsttitle null.

please me form such finallist arraylist.

an idea use mergesort's merge procedure. so, first sort both lists, combine them 1 using conditions you've specified. code after sorting (more or less):

i = 0; j = 0; while (i < m && j < n) {   bean b1 = firstlist.get(i);   bean b2 = secondlist.get(j);   int id1 = b1.getid();   int id2 = b2.getid();   if (id1 < id2) { // id2 bigger, firstlist, increment     finallist.add(new mainbean(id1,b1.gettitle(),null);     i++;   } else if (id1 > id2) { // id1 bigger, secondlist, increment j     finallist.add(new mainbean(id2,null,b2.gettitle()));     j++;   } else { // both same, both, increment both     finallist.add(new mainbean(id1,b1.gettitle(),b2.gettitle()));     i++;     j++;   } } while (i < m) { // take rest of firstlist   bean b = firstlist.get(i);   finallist.add(new mainbean(b.getid(),b.gettitle(),null));   i++; } while (j < n) { // take rest of secondlist   bean b = secondlist.get(j);   finallist.add(new mainbean(b.getid(),null,b.gettitle()));   j++; } 

note:

• m = firstlist.length();
• n = secondlist.length();
• i assume finallist has been initialized before doing procedure