Hughes Systique Software Development Engineer In Test (SDET) interview questions

Interview was quite easy but only 30 mins. ask 1 question from each topic and this doest make sense for me. Ask 2 coding questions but even after explaining the code he want me to execute code online and due to some reason compiler was not able to process Hashmap. Asked diffrence between Arraylist and linkedList and again after giving example he want me to explain more.