Demonstrate how to declare variables and constants in Kotlin, highlighting their differences and use cases.

In Kotlin, variables and constants are declared using the `val` and `var` keywords, respectively. Both variables and constants allow you to store and manipulate data, but they have some key differences in terms of mutability and assignment.

1. Declaring Variables:

* Mutable Variables (`var`): When you declare a variable using the `var` keyword, it means that the variable is mutable, i.e., its value can be changed after it is assigned. You can reassign a new value to a mutable variable multiple times throughout the code.
```
kotlin`var age: Int = 25
age = 26 // Valid: Changing the value of a mutable variable`
```
* Immutable Constants (`val`): Constants, declared using the `val` keyword, are immutable, meaning their value cannot be changed once assigned. Once you assign a value to a constant, it remains constant throughout the code.
```
kotlin`val name: String = "John"
// name = "Mike" // Error: Cannot reassign a value to a constant`
```
2. Use Cases:

* Variables (`var`): Mutable variables (`var`) are useful when you need to store data that can change or be updated. They are suitable for scenarios where the value needs to be modified over time, such as updating a counter or tracking the state of an object. Mutable variables provide flexibility in handling data that undergoes changes during the program's execution.
* Constants (`val`): Immutable constants (`val`) are beneficial when you have data that should remain constant and should not be modified. Constants are ideal for storing values that are not expected to change, such as mathematical constants (e.g., π), configuration values, or values that are determined once and remain unchanged throughout the program's execution. Constants provide clarity and guarantee that the value remains constant, avoiding accidental modifications.
3. Advantages of Immutability:

* Thread Safety: Immutable constants ensure thread safety, as they eliminate the possibility of concurrent modifications. Multiple threads can safely access and use immutable constants without concerns about data corruption or race conditions.
* Code Clarity: Constants provide clarity and self-documentation in code. By using constants, you express the intention that a value should not be changed, making the code more readable and understandable for other developers.
* Optimization Opportunities: The compiler can optimize constant values during compilation, potentially resulting in performance improvements. Immutable constants enable the compiler to make assumptions about the value, leading to more efficient code execution.

When choosing between variables and constants in Kotlin, it's essential to consider the nature of the data and its expected behavior. If a value is not intended to change, using a constant (`val`) helps enforce immutability and ensures data consistency. On the other hand, if a value is expected to change over time, using a variable (`var`) allows for flexibility and dynamic updates. By understanding the differences and use cases of variables and constants in Kotlin, you can make informed decisions when declaring and managing data in your programs.