Apex - Constants

As in any other programming language, Constants are the variables which do not change their value once declared or assigned a value. In Apex, Constants are used when we want to define variables which should have constant value throughout the program execution. Apex constants are declared with the keyword 'final'.

public class CustomerOperationClass {
static final Double regularCustomerDiscount = 0.1;
static Double finalPrice = 0;
public static Double provideDiscount (Integer price) {
//calculate the discount
finalPrice = price - price * regularCustomerDiscount;
return finalPrice;
}
}

Double finalPrice = CustomerOperationClass.provideDiscount(100);
System.debug('finalPrice '+finalPrice);