![\"Fresher-Level](\"https:\/\/www.guvi.in\/blog\/wp-content\/uploads\/2025\/07\/1@2x-1200x630.webp\" "\\"\\"")
<\/figure>\n\n\n\nIf you’re just starting your journey in Java development<\/a>, understanding the core components of the Java Collection Framework is essential. These questions will help you solidify your basics and demonstrate a strong foundational grip during interviews.<\/p>\n\n\n\n The Java Collection Framework (JCF) is a set of classes and interfaces that implement commonly reusable data structures<\/a> such as lists, sets, queues, and maps. It provides algorithms to perform operations like sorting and searching.<\/p>\n\n\n\n HashSet<\/a> uses a HashMap internally to store elements. It ensures uniqueness by using hashCode() and equals() methods to prevent duplicates.<\/p>\n\n\n\n HashMap<\/a> stores data in buckets using an array of Node<K,V>. The key’s hashCode determines the bucket index. If collisions occur, elements are stored in a linked list or balanced tree, depending on the load.<\/p>\n\n\n\n No, a Map cannot have duplicate keys. Each key must be unique, but values can be duplicated.<\/p>\n\n\n\n Some core interfaces include:<\/p>\n\n\n\n The default capacity of an ArrayList is 10<\/strong>.<\/p>\n\n\n\n You can use:<\/p>\n\n\n\n c) ArrayList<\/strong> \u2014 ArrayList allows duplicate elements, unlike Set implementations.<\/p>\n <\/details>\n\n c) Collection<\/strong> \u2014 The Collection interface is the root of the collection hierarchy.<\/p>\n <\/details>\n\n<\/div>\n\n\n\n Once you’re comfortable with the fundamentals, it’s time to dive deeper. These intermediate questions explore more nuanced topics like performance, iteration, and real-world usage of collections, preparing you for hands-on coding and problem-solving scenarios.<\/p>\n\n\n\n Both Iterator and ListIterator are used to iterate through collections, but they differ in capabilities and scope:<\/p>\n\n\n\n If you need more flexibility during traversal, such as moving back and forth or modifying the list structure, ListIterator is preferred.<\/p>\n\n\n\n To remove duplicates from a List, the most straightforward way is to use a Set, since sets don\u2019t allow duplicate elements.<\/p>\n\n\n\n Alternatively, for more control (e.g., using streams):<\/p>\n\n\n\n This is efficient and leverages Java 8+ features.<\/p>\n\n\n\n Fail-safe iterators are more memory-intensive but are safer in multi-threaded environments.<\/p>\n\n\n\n1. What is the Java Collection Framework?<\/strong><\/h3>\n\n\n\n
2. What is the difference between a Collection and a Collections class?<\/strong><\/h3>\n\n\n\n
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<\/li>\n\n\n\n3. What is the difference between List, Set, and Map?<\/strong><\/h3>\n\n\n\n
![\"List,](\"https:\/\/www.guvi.in\/blog\/wp-content\/uploads\/2025\/07\/2@2x-1-1200x630.webp\" "\\"\\"")
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<\/li>\n\n\n\n4. What is the difference between ArrayList and LinkedList?<\/strong><\/h3>\n\n\n\n
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<\/li>\n\n\n\n5. Explain the working of HashSet.<\/strong><\/h3>\n\n\n\n
6. How does HashMap work internally?<\/strong><\/h3>\n\n\n\n
7. Can a Map contain duplicate keys?<\/strong><\/h3>\n\n\n\n
8. What are the main interfaces in the Collection Framework?<\/strong><\/h3>\n\n\n\n
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9. What is the default capacity of an ArrayList?<\/strong><\/h3>\n\n\n\n
10. How do you convert an array to a List?<\/strong><\/h3>\n\n\n\n
List<String> list = Arrays.asList(array);<\/code><\/p>\n\n\n\nTest Your Knowledge: MCQs<\/h2>\n <\/div>\n\n
Q1. Which of the following allows duplicate elements in Java?<\/h4>\n
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\u2705 Answer<\/summary>\n
Q2. Which interface is the root of the Collection hierarchy?<\/h4>\n
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\u2705 Answer<\/summary>\n
Intermediate-Level Java Collection Framework Interview Questions<\/strong><\/h2>\n\n\n\n
![\"Intermediate-Level](\"https:\/\/www.guvi.in\/blog\/wp-content\/uploads\/2025\/07\/3@2x-1-1200x630.webp\" "\\"\\"")
<\/figure>\n\n\n\n11. What is the difference between Iterator and ListIterator?<\/strong><\/h3>\n\n\n\n
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12. How do you remove duplicates from a List in Java?<\/strong><\/h3>\n\n\n\n
List<Integer> list = Arrays.asList(1, 2, 2, 3, 4, 4);\n\nSet<Integer> set = new LinkedHashSet<>(list); \/\/ Maintains insertion order\n\nlist = new ArrayList<>(set);<\/code><\/pre>\n\n\n\nList<Integer> uniqueList = list.stream().distinct().collect(Collectors.toList());<\/code><\/p>\n\n\n\n13. What are fail-fast and fail-safe iterators?<\/strong><\/h3>\n\n\n\n
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14. What is the difference between HashMap and TreeMap?<\/strong><\/h3>\n\n\n\n
![\"Advanced-Level](\"https:\/\/www.guvi.in\/blog\/wp-content\/uploads\/2025\/07\/4@2x-1200x630.webp\" "\\"\\"")
<\/figure>\n\n\n\n![\"Scenario-Based](\"https:\/\/www.guvi.in\/blog\/wp-content\/uploads\/2025\/07\/5@2x-1200x630.webp\" "\\"\\"")
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