The difference between add and AddAll in Java ArrayList

We often have the need to put a list of data into the other list, the most stupid way of course is to add a traversal, but Java provides a AddAll method.

Unlike the Add method, the Add method is to add an item, regardless of what type of data you are, and put it in item as a data add. The AddAll is the same type of data, the existing list is spliced (may not be rigorous). As an example:

There are two lists below, and I want to add the data from the second list to the first list, which is added with the Add method:

for (String item:list2) {

List1.add (item);

}

If you use AddAll:

List1.addall (LIST2);

Isn't it convenient? Of course you can also define the location to add, you can use AddAll (int index, collection<?>);

The difference between add and AddAll in Java ArrayList