What is the Difference Between Array and ArrayList

The main difference between Array and ArrayList is that Array is a fixed length data structure while ArrayList is a variable length Collection class.

Array and ArrayList are commonly used in programming languages such as Java. Array is a data structure that helps to store data elements of the same type. It is static. Therefore, it is not possible to store more elements in it than the declared array size. On the other hand, an ArrayList is a variable length Collection class. Using that class, the programmer can create an ArrayList data structure. The main advantage of an ArrayList is that it is dynamic. Therefore, it is possible to add or remove elements as required.

Key Areas Covered

1. What is Array
     – Definition, Functionality
2. What is ArrayList
    – Definition, Functionality
3. What is the Difference Between Array and ArrayList
     – Comparison of Key Differences

Key Terms

Array, ArrayList, Java

What is Array

An array is a data structure with a fixed length. It helps to store data elements that belong to the same data type. Sometimes, it is required to have many elements of the same data type. For example, assume a program to store marks of students. It is not possible to create variables for each. Array is an alternative to this issue. Using an array, the programmer can store multiple data elements of the same type as a single unit.

int marks[5]; declares an array called marks that can store 5 integer values. The array size is 5. In other words, the array size is fixed. So, the programmer can only store 5 or less elements in that array.  The index of the 1^st element is 0. In this array, the index of the last element is 4. An example program of an array is as follows.

Figure 1: Java program with an Array

In the above program, “marks” is an array. It consists of 5 integers. The for loop iterates through the marks and displays those marks on the console. The sum is an integer type variable which is initialized to zero. The next for loop iterates through the elements of the array. In each iteration, the mark is added to sum. At the end of the for loop, the sum contains the total value of all five marks. Finally, the System.out.println display the total marks.

What is ArrayList

ArrayList is a variable length Collection class. Using this class, the programmer can create an ArrayList data structure. The ArrayList class further implements the List interface. An array is of a fixed length, so it is not possible to store more elements than the defined array size. However, an array list is dynamic. In other words, the programmer can add or remove elements as required. When using ArrayList, the programmer can use predefined methods such as add, remove, etc. Furthermore, it can contain duplicate elements, and it also maintains the data inserted order. An example program is as follows.

Figure 2: Java program with ArrayList

The “numbers” is an object of type ArrayList. The add method allows inserting new elements into the ArrayList. Finally, the for loop iterates through the array list and prints them on the screen. When observing the output, we can see that the ArrayList maintains the data inserted order and it also contains duplicate elements.

Difference Between Array and ArrayList

Definition

An array is a data structure consisting of a collection of elements each identified by the array index. ArrayList, on the other hand, is a class that supports dynamic arrays which can grow as needed. Thus, this is the main difference between Array and ArrayList

Association

Furthermore, while Array is a part of core Java programming, ArrayList is a part of Collection framework with other classes such as Vector, HashMap, etc. Hence, this is also a difference between Array and ArrayList.

Adding Elements

Moreover, in arrays, the programmer can use the assignment operator to store elements into the array. However, in ArrayList, the programmer can use the add method to insert elements.

Consist of

Also, another difference between Array and ArrayList is that an array can contain primitives or objects while an ArrayList can only store objects.

Usage

Besides, Array helps to implement a fixed size data structure whereas arrayList helps to implement dynamic size arrays. So, this is also a difference between Array and ArrayList.

Conclusion

Programming languages such as Java supports Arrays and ArrayLists. The main difference between Array and ArrayList is that Array is a fixed length data structure while ArrayList is a variable length Collection class. In brief, Array has a static nature whereas an ArrayList has a dynamic nature.

Reference:

1. “Java Array – Javatpoint.” Www.javatpoint.com, Available here.
2. “ArrayList in Java – Javatpoint.” Www.javatpoint.com, Available here.