I will quickly explain with an example each collection..
LIST: Is an ordered Collection (sometimes called a sequence). Lists may contain duplicate elements. Elements can be inserted or accessed by their position in the list, using a zero-based index.
- ArrayList
- Advantage: Search. One more advantage is that it is more flexible changing the underlying implementation of an ArrayList, for eg, if you want to make it synchronized, you can convert to a Vector without having to rewrite all the code for an Array.
- Disadvantage: Insert and Delete. ArrayList has a performance limitation. It allocates a particular amount of space... the "capacity". Once you expand the ArrayList to exceed that capacity, the ArrayList has to copy the current array into new memory space, which has a performance hit.
- LinkedList
- Advantage: Insert and Delete. Faster Access time,can be expanded in constant time without memory overhead
- Disadvantage: Search. If using doubly linked list then though it becomes easier to traverse from end but still it increases again storage space for back pointer.
- Vector
- Advantage: Vector is synchronized which means it is suitable for thread-safe operations
- Disadvantage: Poor performance when used in multi-thread environment
SET: Is a Collection that cannot contain duplicate elements. There are three main implementations. Not thread-safe
- HashSet
- Advantage: Insert and Search. One more advantage is that it operates in constant time, as opposed to the O(log N) time for the Set class.
- Disadvantage: Is that iterators return the values in a seemingly random order.
- LinkedHashSet
- Advantage: Elements gets sorted in the same sequence in which they have been added to the Set.
- Disadvantage: Iteration performance
- TreeSet
- Advantage: Elements gets sorted in the same sequence in which they have been added to the Set.
- Disadvantage: If you don’t supply a Comparator to define the ordering you want, TreeSet requires a Comparable implementation on the item class to define the natural order
MAP: Is an object that maps keys to values. A map cannot contain duplicate keys. There are three main implementations of Map interfaces
- HashMap
- Advantage: Used for storing Key & value pairs. permits nulls(null values and null key)
- Disadvantage: There's also the potential for collisions. The cost of writing and/or executing the hashing-function could be high if the requirement for collision avoidance is strict, or if you have a small hash-space.
- TreeMap
- Advantage: Is that it allows to store the key-value mappings in a sorted order. Treemap internally uses red black tree.
- Disadvantage: No guarantees concerning the order of iteration.
- LinkedHashMap
- Advantage: Allows predictable iteration order
- Disadvantage: Memory usage and probably higher insertion cost
Conclusion
Whatever the application you are working, always try to use the best possible approach. There are different types of collections for use in differente situations, so do not hesitate. Think of the approach and choose the best possible option.
GitHub: https://github.com/mateusmachado/PocCollectionsJava
