Understanding Double Values in Apex

In Apex, the Double data type is used to store numbers that have decimal places. Think of it like a calculator where you can have numbers like 3.14 or 99.99.

Declaring and Setting Double Variables

You can create a Double variable and give it a value in a few ways.

// Declare a variable called 'price' and set its value
Double price = 10.50;

// Declare a variable first, then set its value later
Double quantity;
quantity = 5.0;

// Use the Double.valueOf() method to convert text or another number to a Double
Double taxRate = Double.valueOf('0.07'); // Convert text '0.07' to a Double
Double itemCount = Double.valueOf(10); // Convert the number 10 to a Double (becomes 10.0)

Notice that even if you set a Double to a whole number like 10, Apex will still store it with a decimal, like 10.0.

Doing Simple Math with Doubles

You can use Double variables to do basic calculations:

Double item1Price = 5.99;
Double item2Price = 12.50;

// Addition (+)
Double subtotal = item1Price + item2Price; // subtotal will be 18.49

Double totalItems = 25.0;
Double itemsSold = 10.0;

// Subtraction (-)
Double itemsRemaining = totalItems - itemsSold; // itemsRemaining will be 15.0

Double numberOfOranges = 3.0;
Double pricePerOrange = 0.75;

// Multiplication (*)
Double costOfOranges = numberOfOranges * pricePerOrange; // costOfOranges will be 2.25

Double totalDistance = 100.0; // in kilometers
Double timeTaken = 2.5; // in hours

// Division (/)
Double averageSpeed = totalDistance / timeTaken; // averageSpeed will be 40.0

Double vs. Decimal (Quick Note)

Both Double and Decimal can store numbers with decimals, but they are used for different things, especially in Salesforce:

• Double: Good for general numbers with decimals, like measurements or quantities. It's generally faster for calculations.
• Decimal: Very important for working with money or anything that needs exact precision. Double can sometimes have tiny rounding issues that you don't want with currency. We'll learn more about Decimal later!

For now, focus on using Double for simple numbers with decimal places and basic math.

Best Practice

• Use Double when you need to store numbers with decimal points and are doing general calculations (not money).

By practicing with these basics, you'll get comfortable using Double values in your Apex code!