Java - no_image

• Resizable: Array is static in size that is fixed length data structure, one cannot change the length after creating the Array object. ArrayList is dynamic in size. Each ArrayList object has instance variable capacity which indicates the size of the ArrayList. As elements are added to an ArrayList its capacity grows automatically.

• Performance: Performance of Array and ArrayList depends on the operation you are performing:
  1. resize() opertation : Automatic resize of ArrayList will slow down the performance as it will use temporary array to copy elements from the old array to new array. ArrayList is internally backed by Array during resizing as it calls the native implemented method System.arrayCopy(src,srcPos,dest,destPos,length).
  2. add() or get() operation : adding an element or retrieving an element from the array or arraylist object has almost same performance , as for ArrayList object these operations run in constant time.

• Primitives: ArrayList cannot contains primitive data types (like int, float, double) it can only contains Object while Array can contain both primitive data types as well as objects. One get a misconception that we can store primitives(int,float,double) in ArrayList , but it is not true

• Type-Safety: In Java, one can ensure Type Safety through Generics. while Array is a homogeneous data structure, thus it will contain objects of specific class or primitives of specific data type. In array if one tries to store the different data type other than the specified while creating the array object, ArrayStoreException is thrown.

• Multi-dimensional: Array can be multi-dimensional, while ArrayList is always single dimensional.

• Adding elements: We can insert elements into the ArrayList object using the add() method while in array we insert elements using the assignment operator.

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