Declare Apex Variable

Declaring Variables in Apex, Saelsforce (SFDC)

You can declare variables in Apex like any other programming language in simple way - like String and Integer as follows : 

    //String variable declaration with value = 'my string'
    String str = 'my string'; 

    
    // Integer variable declaration with value = 9 
         Integer i = 9;  

* Remember Apex variables are Case-Insensitive