Salesforce Platform Developer I Certification Guide

Apex data types

Each variable in Apex has a data type. This can be a primitive data type (such as String, Decimal, and so on), an sObject, an enum, an Apex class, or a collection of these types.

The following table will give you an overview of all the different variable types you can use in Apex:

Blob	Binary data is being stored as a single object. By using the toString() or valueOf() methods, you can convert this data type to a string. Examples of a blob are web service arguments, the content of a document, and attachments.
Boolean	A value that can correspond to a checkbox. The value can only be true, false, or null.
Date	A variable that contains a day as a value. Date values must initiate the system static method (Date.newInstance(Year, ...