apex trigger error on leads object

Question

hi m getting the error while in one video the same code is working fine

****Error: Compile Error: expecting an equals sign, found '1' at line 2 column 14****

trigger HelloWorld on Lead (before update) {
    for (Lead 1 = Trigger.new) {
    1.FirstName = 'Hello';
    1.LAstName  = 'World';
   }
}

Answer 1

couple of errors here

trigger HelloWorld on Lead (before update) {
    //here this should colon not equal in loop 
    // don't use integer here instead use l as variable 
    for (Lead l : Trigger.new) {
    l.FirstName = 'Hello';
    l.LAstName  = 'World';
   }
}

Answer 2

Every programming language has its own set of rules and conventions for the kinds of names that you're allowed to use.

I was trying to find out any Salesforce document which provides information about naming convention but i didn't find one.But it is said that they are similar like JAVA.So adding information about naming convention from Java docs.

1. A variable’s name can be any legal identifier.

2. It can contain Unicode letter,Digits and Two Special Characters such as Underscore and dollar Sign.

3. Length of Variable name can be any number.
4. Its necessary to use Alphabet at the start (however we can use underscore , but do not use it )
5. Some auto generated variables may contain ‘$‘ sign. But try to avoid using Dollar Sign.
6. White space is not permitted.
7. Special Characters are not allowed.

and finally

8. Digit at start is not allowed.

Documentation