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Many people and authors suggested to us to use list than array.
List <Integer> list = new ArrayList<Integer>();
list.addElement(1);
....
What it is the reason behind it?
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It's better to use an ArrayList if you don't know, in advance, how many elements there are going to be. The ArrayList correctly amortizes the cost of growing the backing array as you add more elements to it, and is suitable for random access once the elements are in place. An ArrayList can be efficiently sorted.
Conclusion: set operations on arrays are about 40% faster than on lists, but, as for get, each set operation takes a few nanoseconds - so for the difference to reach 1 second, one would need to set items in the list/array hundreds of millions of times!
An Array is a collection of similar items. Whereas ArrayList can hold item of different types. An array is faster and that is because ArrayList uses a fixed amount of array.
List in Java provides the facility to maintain the ordered collection. It contains the index-based methods to insert, update, delete and search the elements. It can have the duplicate elements also. We can also store the null elements in the list.
You should generally prefer to choose the right data structure for the job. You need to understand your task at hand as well as all the different options you have and how they compare in terms of iteration, and searching, and adding, removing, and inserting data. In general, you need to understand how the data structure accesses and manipulates memory and choose the best data structure based on how you anticipate your application will be used.
Obviously, it isn't always clear-cut. But you can understand the ideals for different data structures.
For example, purely static, fixed length data in which you'll only iterate, without a need for search, is ideal for an array. It's common to use such arrays in cipher algorithms. If the data is static but instead of iterating, you need to search, you might want some type of tree structure. If you want fast insertion, hashing is probably the ideal. If the data changes often, you want a structure that is efficient at changing its size, like a list.
Of course, there's many variations and combinations of data structures designed to solve all kinds of specific problems. The reason there are so many is because of the importance they play in writing efficient programs. Anyway, my point is, learn about data structures. Understand the ideal situations for each and then you'll be able to decide or design suitable data structures for any task.
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