Learning Jupyter 5 - Second Edition

Scala immutability

Immutable means you cannot change something. In Scala, all variables are immutable, unless specifically marked otherwise. This is the opposite to languages such as Java, where all variables are mutable unless specifically marked otherwise.

In Java, we can have the following function:

public void calculate(integer amount) { 
} 

We can modify the value of amount inside the calculate function. We can tell Java not to allow changing the value if we use the final keyword, as in:

public void calculate(final integer amount) { 
} 

Whereas in Scala:

def calculate (amount: Int): Int = {  
        amount = amount + 1; 
        return amount; 
} var balance = 100val result = calculate(balance)

A similar routine leaves the value of the amount variable as ...