Question

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ArrayList declaration Java

In Java, why is an ArrayList often declared using a List?

List<String> strList1 = new ArrayList<String>();
ArrayList<String> strList2 = new ArrayList<String>();

I am not able to understand the difference between these two. Is one better than the other? or have a specific use?

Answer 1

The ArrayList class implements the List interface.

It is usually a good practice to declare an object of the type of the interface and of course instantiate it using an implementation of that interface.

This way, you can change the implementation when needed, but the declared type stays unchanged. This way, you could avoid modifying too much code especially in the methods getting the variable as a parameter. The method keeps getting a List as a parameter, not a certain implementation.