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How to concat two ArrayLists?

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伪装坚强ぢ
伪装坚强ぢ 2020-12-13 23:29

I have two ArrayLists of equal size. List 1 consists of 10 names and list 2 consists of their phone numbers.

I want to concat the names and number into

7条回答
  • 予麋鹿
    予麋鹿 (楼主)
    2020-12-14 00:14

    for a lightweight list that does not copy the entries, you may use sth like this:

    List mergedList = new ConcatList<>(list1, list2);



    here the implementation:
    


    public class ConcatList extends AbstractList {

    private final List list1;
    private final List list2;

    public ConcatList(final List list1, final List list2) {
        this.list1 = list1;
        this.list2 = list2;
    }

    @Override
    public E get(final int index) {
        return getList(index).get(getListIndex(index));
    }

    @Override
    public E set(final int index, final E element) {
        return getList(index).set(getListIndex(index), element);
    }

    @Override
    public void add(final int index, final E element) {
        getList(index).add(getListIndex(index), element);
    }

    @Override
    public E remove(final int index) {
        return getList(index).remove(getListIndex(index));
    }

    @Override
    public int size() {
        return list1.size() + list2.size();
    }

    @Override
    public void clear() {
        list1.clear();
        list2.clear();
    }

    private int getListIndex(final int index) {
        final int size1 = list1.size();
        return index >= size1 ? index - size1 : index;
    }

    private List getList(final int index) {
        return index >= list1.size() ? list2 : list1;
    }

}

    
    
    
             
    
                                                        
    
            
            
    
              
                
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