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Exploring Java Collections: Interfaces, Generics, and Data Structure Trade-offs

Dive into the fundamentals of Java Collections in this informative session. We'll cover important concepts like the Java Collection Interface, the usage of generics, and the significance of wrapper classes. Learn about the distinctions between lists, sets, stacks, queues, and maps, including their basic operations and unique characteristics. Discover how Java handles autoboxing and unboxing for primitive types, and understand when to use different types of collections. Join us for a comprehensive overview of effective collection management in Java!

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Exploring Java Collections: Interfaces, Generics, and Data Structure Trade-offs

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Presentation Transcript

  1. CSE373 Optional Section Java Collections 11/12/2013 Luyi Lu

  2. Today’s Topic • Java Collection Interface • Generics Collections Usage • Wrapper Class • CSE 142/143 Collections Review • List & Set • Stack & Queue • Map

  3. JavaCollectionInterface • Interface is just a type • LearnhowtolookupJava Documentation of the standard library • What are the basic operations? • http://docs.oracle.com/javase/7/docs/api/java/util/Collection.html • Iterable<E> and Comparable<E> • Touseforloopanddefine the rule how object stored is compared • Not used in HW5, but good to know

  4. CollectionsDeclarationwithGeneric Types • How? • List<Vertex> v = new ArrayList<Vertex>(); • List<Edge> e = new ArrayList<Edge>(); • Can we construct List ArrayList<int>? • NO! In Java, anything that is used as generics has to be convertible to Object • Solution: Use Wrapper Class for primitive types. E.g. ArrayList<Integer> • Every primitive type has a corresponding wrapper class: • Integer for int, • Double for double, • Character for char, • Boolean for boolean, • And so on • BTW.. String is not a primitive type and String objects are immutable • (Continue on next slide)

  5. CollectionsDeclarationwithGeneric Types • Autoboxing and Unboxing • Java will automatically "box" the ints for us (i.e., wrap them up in Integer objects) • Java automatically "unboxes" the values for you, unwrapping the Integer objects and giving you the ints that are contained inside. List<Integer> numbers1 = new ArrayList<Integer>(); numbers.add(18); numbers.add(34); int product = numbers.get(0) * numbers.get(1);

  6. Lists& Sets • Difference? • Sets don’t allow duplicates • Client can control order over lists, no index (How to remove?) • HashSetdoesn’t keep order • TreeSet keeps things in sorted order • APIs • List: http://docs.oracle.com/javase/7/docs/api/java/util/List.html • Set: http://docs.oracle.com/javase/7/docs/api/java/util/Set.html • Different Types and their Tradeoffs • List • ArrayList • LinkedList • Set • HashSet(fast) • TreeSet • Declaration: LinkedList<E> l = LinkedList<E>(); is not good style • should be List<E> l = LinkedList<E>(); You can find all of them in JAVA API!

  7. Stack & Queue • Discussed in CSE373 • APIs • Stack Class: http://docs.oracle.com/javase/7/docs/api/java/util/Stack.html • Stack<E> s = new Stack<E>(); • Queue Interface: http://docs.oracle.com/javase/7/docs/api/java/util/Queue.html • Queue<E> q = new LinkedList<E>();

  8. Map • Dictionary that stores key/value pairs • One to one relation • Map<K,V>canhavetwotypes.You can have V as Lists or other data structures • E.g. Map<String, Set<String>> • API: http://docs.oracle.com/javase/7/docs/api/java/util/Map.html • TreeMapandHashMap

  9. Useful Info ArrayList vs. Linked List http://stackoverflow.com/questions/322715/when-to-use-linkedlist-over-arraylist HashSet vs. TreeSet http://stackoverflow.com/questions/1463284/hashset-vs-treeset Some material of this slideis credited to Stuart Reges’ CSE143 Notes

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