Add all the elements of multiple ArrayList objects into a single ArrayList object

Question

In my case I have 4 ArrayList objects as below:

ArrayList<MyProduct> lstStyle;
ArrayList<MyProduct> 2ndStyle;
ArrayList<MyProduct> 3rdStyle;
ArrayList<MyProduct> 4thStyle;

I want to add all the elements in each ArrayList into a new ArrayList called Style .

ArrayList<MyProduct> Style;

Can I do this without looping each ArrayList?

Answer 1

Use the List#addAll(Collection c) method

Style.addAll(lstStyle);
Style.addAll(2ndStyle);
Style.addAll(3rdStyle);
Style.addAll(4thStyle);

Ofcourse, you need to instantiate all the lists first, otherwise you'll face a NullPointerException .

Answer 2

Collections.addAll(Style, lstStyle, 2ndStyle, 3rdStyle, 34thStyle);

Answer 3

Use addAll method

ArrayList<MyProduct> Style;

 Style.addAll(lstStyle);
 Style.addAll(2ndStyle);
 Style.addAll(3rdStyle);
 Style.addAll(4thStyle);