I think there is no exact answer, since every companies has their own standard as well as their own strategy in hiring people but still I would like to highlight few points here. You are expected to know following things as junior developers: Java basics : As you know Java is an Object oriented programming language, you need to understand object oriented concepts such as abstraction, encapsulation, polymorphism, and inheritance. You might not have used all the object oriented concepts as junior developer but you should know about it. Collections: Collections framework is the most used framework in Java.Don't just understand the usage of collections such as HashMap, HashSet, TreeMap, Treeset but also understand internal working of Collections. It is enough to just understand usage of these collections but it will be better if you know internals of it, it increases chances of selection in interview. Multithreading: You should know basics of threads such as how to create a thread, life cycle of thread and different methods of Thread class such join, sleep, yield. Basic data structures: You should be able to write and understand basic data structures such as List, Queue, Stack, HashMap, LinkedList. etc. Basic Programs: You should be able to write basic java programs on String, Numbers and Array etc. Joe has already shared some good links, I would like to add few more. https://www.javatpoint.com/corejava-interview-questions Core Java interview questions and answers http://career.guru99.com/top-100-core-java-interview-questions/