Difference between Array and ArrayList
Arrays and ArrayLists are both used to store collections of elements in Java, but they have several differences in terms of their characteristics, capabilities, and usage. Here’s a comparison between Arrays and ArrayLists:

Table of Contents
1. Data Structure:
- Array: Arrays are fixed-size data structures that store elements of the same type in contiguous memory locations. Once created, the size of an array cannot be changed.
- ArrayList: ArrayLists are dynamic arrays that can grow or shrink in size as needed. They internally use an array but provide methods to dynamically resize it.
2. Size:
- Array: The size of an array is fixed and specified at the time of creation. It cannot be changed later.
- ArrayList: ArrayLists can dynamically adjust their size as elements are added or removed. They automatically resize their internal array as needed.
3. Type Safety:
- Array: Arrays can hold elements of primitive data types (e.g., int[], double[]) as well as objects (e.g., String[]). They provide type safety at compile time.
- ArrayList: ArrayLists can only hold objects (including wrapper classes for primitive types). They provide type safety through generics, ensuring that only elements of the specified type can be added.
4. Performance:
- Array: Arrays generally offer better performance for random access and element retrieval, as they directly access memory locations using index positions.
- ArrayList: ArrayLists are slower for random access compared to arrays because they involve an additional level of indirection through method calls.
5. Usage:
- Array: Arrays are suitable when the size is known in advance and remains constant throughout the program execution. They are commonly used for fixed-size collections.
- ArrayList: ArrayLists are preferred when the size of the collection may change dynamically during runtime. They are commonly used for resizable collections where flexibility is required.
6. Mutability:
- Array: Once created, the elements of an array cannot be added, removed, or replaced. However, individual elements can be modified.
- ArrayList: ArrayLists provide methods to add, remove, and replace elements dynamically, allowing for easy manipulation of the collection.
7. Syntax:
- Array: Arrays are declared using square brackets ([]) with the element type and size specified. Example: `int[] arr = new int[5];`
- ArrayList: ArrayLists are declared using the `ArrayList` class with the element type specified using generics. Example: `ArrayList<Integer> list = new ArrayList<>();`
Summary:
Arrays and ArrayLists both serve as containers for storing collections of elements, but they differ in terms of mutability, size flexibility, type safety, and performance characteristics. Arrays are fixed-size and offer better performance for random access, while ArrayLists are dynamic and provide flexibility for resizing the collection at runtime. The choice between the two depends on the specific requirements and constraints of the application.