5 JAVA Interview Questions (With Example Answers)
- 1 What are the benefits of Java Collections Framework?
This question may be asked early in a series of Java Collections interview questions because it requires only a basic knowledge of the system to answer. While it may be a segue into more complex questions, it is still important to speak from experience that displays your expertise and passion.
Example: “The benefits of Java Collections Framework include highly efficient performance, reusability, ease of maintenance and opportunities to customize collection types. In my experience as a Java developer, I found the customization to be handy.
- 2 What is the technical difference between a Collection and Collections Framework?
This question also helps to establish the level of technical knowledge you have about the system. In this case, being clear and concise with each definition should show the interviewer that you know the distinction between the terms.
Example: “A Collection is a contained object that holds the many elements required to create an application or script. The Collections Framework is the system of collections that allows for the centralized management and maintenance of each one.”
- 3 What are the main interfaces used in the Java Collections Framework? Describe each
This technical question requires a more complex answer, and to be thorough, you should respond to it thoughtfully and in multiple parts. In the first part of the answer, you should list all five primary interfaces. In the second part of the answer, you should define them.
Example: “The five primary interfaces of the Java Collections Framework are the Collection Interface, Set Interface, Queue Interface, List Interface and Map Interface. Using these collections, developers can make several applications. The Collection Interface is the core of the framework and the foundation upon which most projects are built. Set Interface is similar to Set command, and it doesn’t allow for index-based searches or duplicate entries. The Queue Interface stores entries in a queue based on the order they were entered. List Interfaces are ordered and contain duplicate entries if desired. Key-value pairing is essential to the Map Interface, which is a data structure that doesn’t allow duplicates as a requirement.”
- 4 Explain in basic terms the meaning of iterator and enumeration, as if talking to a board member
Whenever you are asked to explain a concept “in simple terms” or “in basic terms” in a technical interview, frame your answer in a way that is easy for people without a technical background to understand. In this case, the interviewer is giving you an additional piece of information: they are asking you to speak on the subject like you are talking to a board member. This should indicate that clarity and professionalism are key in this response.
Example: “In Java, iterator and enumeration are interfaces that allow you to browse, or iterate, a Collection to examine all of its elements. While they both serve the same basic purpose, the iterator has more advanced features than enumeration. For example, it can remove an element from the Collection.”
- 5 How would you explain removing redundant elements from an ArrayList object to a member of your team?
This question is similar to the last in that it asks you to explain a technical process in clear terms. The difference, however, is that you are explaining it to a colleague in information technology. This could be someone you manage or someone who supervises you, but, ultimately, it is someone on your team who knows technical principles. In this case, it is crucial to display your ability to communicate clearly and effectively with a team.
Example: “To remove the redundant element from the ArrayList, you should follow three steps. First, offload elements in the ArrayList to a LinkedHashSet. Next, make sure the ArrayList is empty, and finally, copy all elements of the LinkedHashSet back to an ArrayList.”