Can you tell me the differences between Array and ArrayList?

Can you tell me the differences between Array and ArrayList?

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    Difference between Array and ArrayList in Java with Example

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

    2. Performance : Performance of Array and ArrayList depends on the operation you are performing :

    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) .
    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.

    3. Primitives :  ArrayList can not 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

    Suppose we have ArrayList object ,

    ArrayList  arraylistobject = new ArrayList();
    arraylistobject.add(23);  // try to add 23 (primitive)

    JVM through Autoboxing(converting primitives to equivalent objects internally) ensures that only objects are added to the arraylist object.
    thus , above step internally works like this :

    arraylistobject.add( new Integer(23));
    // Converted int primitive to Integer object and added to arraylistobject

    4. Iterating the values : We can use iterator  to iterate through ArrayList . The iterators returned by the ArrayList class’s iterator and listiterator method are fail-fast.  We can use for loop or for each loop to iterate through array .

    5. 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 try to store the different data type other than the specified while creating the array object , ArrayStoreException is thrown.

    for example :

    String temp[] =  new String[2];  // creates a string array of size 2
    temp[0] = new Integer(12); // throws ArrayStoreException, trying to add Integer object in String[]

    6. Length :  Length of the ArrayList is provided by the size() method while Each array object has the length variable which returns the length of the array.

    for example :

    Integer arrayobject[] = new Integer[3];
    arraylength= arrayobject.length   ;  //uses arrayobject length variable


    ArrayList  arraylistobject = new ArrayList();
    arraylistobject.size();   //uses arraylistobject size method

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

    for example :

    Integer addarrayobject[] = new Integer[3];
    addarrayobject[0]= new Integer(8)   ;  //new object is added to the array object

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

    example of multidimensional array:

    Integer addarrayobject[][] = new Integer[3][2];
    addarrayobject[0][0]= new Integer(8)
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    Answered on February 19, 2019.
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    Array vs ArrayList in Java
    1) First and Major difference between Array and ArrayList in Java is that Array is a fixed length data structure while ArrayList is a variable length Collection class. You can not change length of Array once created in Java but ArrayList re-size itself when gets full depending upon capacity and load factor. Since ArrayList is internally backed by Array in Java, any resize operation in ArrayList will slow down performance as it involves creating new Array and copying content from old array to new array.

    2) Another difference between Array and ArrayList in Java is that you can not use Generics along with Array, as Array instance knows about what kind of type it can hold and throws ArrayStoreException, if you try to store type which is not convertible into type of Array. ArrayList allows you to use Generics to ensure type-safety.

    3) You can also compare Array vs ArrayList on How to calculate length of Array or size of ArrayList. All kinds of Array provides length variable which denotes length of Array while ArrayList provides size() method to calculate size of ArrayList in Java.

    4) One more major difference between ArrayList and Array is that, you can not store primitives in ArrayList, it can only contain Objects. While Array can contain both primitives and Objects in Java. Though Autoboxing of Java 5 may give you an impression of storing primitives in ArrayList, it actually automatically converts primitives to Object. e.g.

    ArrayList integerList = new ArrayList();
    integerList.add(1); //here we are not storing primitive in ArrayList, instead autoboxing will convert int primitive to Integer object

    5) Java provides add() method to insert element into ArrayList and you can simply use assignment operator to store element into Array e.g. In order to store Object to specified position use

    Object[] objArray = new Object[10];
    objArray[1] = new Object();

    6) One more difference on Array vs ArrayList is that you can create instance of ArrayList without specifying size, Java will create Array List with default size but its mandatory to provide size of Array while creating either directly or indirectly by initializing Array while creating it. By the way you can also initialize ArrayList while creating it.

    Difference between Array and ArrayList in Java with exampleThat’s all on difference between Array and ArrayList in Java. In terms of performance Array and ArrayList provides similar performance in terms of constant time for adding or getting element if you know index. Though automatic resize of ArrayList may slow down insertion a bit Both Array and ArrayList is core concept of Java and any serious Java programmer must be familiar with these differences between Array and ArrayList or in more general Array vs list

    Answered on February 19, 2019.
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    Arrays are strongly-typed collections of the same data type and have a fixed length that cannot be changed during runtime. We can access the Array elements by numeric index. The array indexes start at zero. The default value of numeric array elements is set to zero, and the reference elements are set to null.





    An Array list is not a strongly-typed collection. It can store the values of different data types or same datatype. The size of an array list increases or decreases dynamically so it can take any size of values from any data type. ArrayList is one of the most flexible data structures from C# Collections. ArrayList contains a simple list of values. ArrayList implements the IList interface using an array and very easily we can add, insert, delete, view etc. It is very flexible because we can add without any size information that is it will grow dynamically and also shrink.




    Answered on February 20, 2019.
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    One more major difference between ArrayList and Array is that, you can not store primitives in ArrayList, it can only contain Objects. … In terms of performanceArray and ArrayList provides similar performance in terms of constant time for adding or getting element if you know index.

    Answered on February 21, 2019.
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