@CheckForNull
public Object canReturnNull(){
    return null;
}

public Object canAlsoReturnNull(){
    return null;
}

public void testMethod(){
    if(canReturnNull()!=null){
        Class cls = canReturnNull().getClass(); //Sonar complains about possible NP
    }
    if(canAlsoReturnNull()!=null){
        Class cls = canAlsoReturnNull().getClass(); //Sonar does not complain about possible NP
    }
}

public void testMethod2(){
    Object o = canReturnNull();
    if(o !=null){
        Class cls = o.getClass(); //Sonar does not complain anymore
    }
    if(canAlsoReturnNull()!=null){
        Class cls = canAlsoReturnNull().getClass(); //Sonar does not complain about possible NP
    }
}