merge two arraylist lists in list1 while it remain sorted

Question

In my assignment the third step is to Call the method merge to merge the two lists in list1 so that the list1 remains sorted.

I write my code but it

Answer 1

     ArrayList<Integer> a = new ArrayList();
     ArrayList<Integer> b = new ArrayList();
     ArrayList<Integer> c = new ArrayList();

     a.add(1);
     a.add(3);
     a.add(5);
     a.add(7);
     a.add(17);
     a.add(27);
     a.add(37);

     b.add(0); 
     b.add(2);
     b.add(4);

     while( a.size() > 0 || b.size() >0){

        if( a.size() == 0 || b.size() == 0){
            c.addAll(b);
            c.addAll(a);
            break;
        }

        if(a.get(0) < b.get(0)){
            c.add(a.get(0));
            a.remove(0);
        }
        else{
            c.add(b.get(0));
            b.remove(0);
        }

    }

    System.out.println(c.toString());

Answer 2

After you merge the lists, call sort method as below.

Collections.sort(list1); // carries out natural ordering.

If you need a customized sorting, use Comparator object

Collections.sort(list1, comparatorObject);

Check Comparator example for more details.

Here is your modified code:

 public static void merge (ArrayList<Integer> list1, ArrayList<Integer> list2)
 {
    list1.add(list2); //merges list 2 to list1
    Collections.sort(list1); //natural ordering
 }

Answer 3

Easy fix: sort afterwards.

list1.addAll(list2);
Collections.sort(list1);

Use sets to avoid duplicates.

Answer 4

public static void merge (ArrayList<Integer> list1, ArrayList<Integer> list2)
{
    list1.addAll(list2);
    Collections.sort(list1);
}

Answer 5

If your input Lists aren't too long, I'd suggest just merging the lists and using the Collections.sort() Method to restore the order:

public static void mergeAndSort(List<Integer> list1, List<Integer> list2) {
    List<Integer> combinedList = new ArrayList<Integer>(list1);
    combinedList.addAll(list2);
    Collections.sort(combinedList);
    return combinedList;
}

As a sidenote, you should use the List interface instead of the ArrayList implementation class wherever possible.

Answer 6

public list mergeAndSort(List<integer> list1, List<integer> list2){
List<integer> list3;
int list2Size = list2.size();
for(int i=0;i<list2Size;i++){
    list1.add(list2(i));  
}
// Here we got all the elements in 1 list i.e list1

int list1Size = list1.size();
for(i=0;i<list1Size;i++){
    int small = 0;
    for(int j=i;j<list1size;j++){
        if(list1(i)> list2(j)){
            small = list2(j;
        }
    }
    list3.add(small); //Smallest 1 will be added to the new list
}

}