In Java, ArrayList and HashMap are the two generally used classes of the Java Collection Framework. Indeed by both are the part of the Collection frame, how they store and reuse the data is different.
The difference between ArrayList and HashMap is that ArrayList is an indicator- grounded data- structure supported by array, while the HashMap is a counterplotted data structure, which works on mincing to recoup stored values. Although both are used to store objects, they’re different in their perpetration, function, and operation.
ArrayList vs. HashMap
It will help you to which collection class is suitable for a particular use:
ArrayList |
HashMap |
| – Implements the List interface. | – Implements the Map interface. |
| – Stores element‘s value and maintains the indicators for each element. | – Stores rudiments crucial & value brace. For each value, there must be a key associated with HashMap. |
| – Stores only a single object. | – Stores rudiments in Key and value pairs. |
| – We get the element by specifying the indicator of it in ArrayList. | – The rudiments are being brought by the corresponding crucial in HashMap. |
| – The ArrayList maintains the order of the objects they’re fitted. | – HashMap doesn’t give a guarantee of the order in which they’re fitted . |
| – ArrayList allows indistinguishable rudiments. | – HashMap allows indistinguishable values but doesn’t allow indistinguishable keys. |
| – The ArrayList always gives O( 1) performance in stylish case or worst- case time complexity. | – The HashMap get() system has O( 1) time complexity in the stylish case and O( n) time complexity in worst case. |
| – ArrayList has any number of null rudiments. | – HashMap allows only one null crucial and lots of null values. |
| – ArrayList is the indicator- grounded data stricture supported by the array. | – While HashMap is a counterplotted data structure that works on mincing to gain stored values. |
It’s each about the differences between ArrayList and HashMap. They both are different from each other and work for a differentpurpose.However, use HashMap if we need mapping keys to values and using ArrayList, If you’re looking to store objects in Java.
The similarity between ArrayList and HashMap
1. Both aren’t accompanied; We can not use them in amulti-threading terrain without any external synchronization.
2. Both ArrayList and HashMap Iterator are fail-fast. It throws ConcurrentModification Exception and detect the structural changes the iterator is created in ArrayList or HashMap.
3. Allows both ArrayList and HashMap null. HashMap allows null keys and values.
4. Both uses the progeny() system. TheArrayList.get() system works grounded on the indicator and HashMap.get() system takes a parameterkey_element of object type and refers to the key which associated value is brought. thus, they both provides constant- time performance.
5. An array supports ArrayList. also, HashMap is also internally enforced by array.
6. We use Iterator for penetrating the rudiments of ArrayList and HashMap.
