A list of funny and tricky Apex examples

Inspired by wtfjs

Boolean b;
if(b!=true) system.debug(‘b is not true’);
if(b!=false) system.debug(‘b is not false’);

See Advanced Apex Programming in Salesforce for explination.

String x = 'Abc';
String y = 'abc';
System.assert(x == y); // passes
System.assertEquals(x, y); // fails

Explanation

Nothing prevents you from recreating a class with the same name of one that exists in the System (default) namespace.

public class Database {
    public static List<sObject> query(String qry){
        System.debug(qry);
        return null;
    }
}

Running Database.query('foo') will call our new class (essentially override the Database methods!?)

source

public class IExist{}
System.assertEquals(IExist.class, IExist.IDont.Class); //passes

Source: Kevin Jones

In their naming conventions:

public class OhGodBees extends Exception{}
//fails: OhGodBees: Classes extending Exception must have a name ending in 'Exception'

Constructors:

public class BeesException extends Exception{
    public BeesException(){}
}
//fails: System exception constructor already defined: <Constructor>()

For Explination see

Database.query is one of many cases where the salesforce "System" namespace doesn't play by it's own rules. It can either return a List<SObject> or a single SObject. No Casting required.

Foo__c foo = Database.Query('SELECT Id FROM Foo__c');
List<Foo__c> foos = Database.Query('SELECT Id FROM Foo__c');

Try writing your own method to do this and you'll get a error:

Method already defined: query SObject Database.query(String) from the type Database (7:27)

You can overload arguments, but not return type.

If you write an If/Else without braces, symbols scoped in the "if" seem to leak into the "else":

if(false)
   String a = 'Never going to happen.';
else
   a = 'I should not compile';

Worth noting that Java won't even allow you to declare a block scoped variable inside a "braceless IF" as it can never be referenced elsewhere.

Source: Kevin Jones

A Set can be iterated in a for loop:

Set<String> mySet = new Set<String>{'a', 'b'};
for(String s : mySet){}

But it doesn't implement the Iterable interface:

String.join(mySet, ',');
/// fails because Set doesn't implement Iterable
String.join((Iterable<String>) mySet, ',');
/// or does it? This cast succeeds!

Enums in batch

Objects in hascodes

1. There way to control automatic serialization of object properties (like [JsonProperty(PropertyName = "FooBar")] in C#)
2. There are reserved keywords that you can't use as property names.

Meaning the following cannot be parsed or generated using JSON.deserialize or JSON.serialize:

{
   "msg": "hello dingus",
   "from": "Dr. Dingus"
}

Work Around

Apperently once upon a time, generics were part of apex. However, they have since been removed (with the exception of system classes (List<>, Batchable<>, etc).

Why would you want generics when you're OS has perfectly good Copy & Paste functionality built right into it?

Vote for Generics

public abstract class ImAbstract {
    public String foo;
}

ImAbstract orAmI = (ImAbstract) JSON.deserialize('{"foo":"bar"}', ImAbstract.class);
System.debug(orAmI.foo);

source

Object x = 42;
System.debug(x instanceOf Integer); // true
System.debug(x instanceOf Long);  // true
System.debug(x instanceOf Double);  // true
System.debug(x instanceOf Decimal); // true

Source Dainel Barrileger

Thankfully these WTF's have since been fixed by Salesforce. We'll keep them documented for historical purposes (and entertainment).

https://twitter.com/FishOfPrey/status/869381316105588736

https://twitter.com/FishOfPrey/status/1016821563675459585 https://salesforce.stackexchange.com/questions/224490/bug-in-list-contains-for-id-data-type