The java.util.ListIterator is an iterator for lists that allows the programmer to traverse the list in either direction (i.e. forward and or backward) and modify the list during iteration. What are the benefits of the Java Collections Framework? Collections framework provides flexibility, performance, and robustness. Polymorphic algorithms – sorting, shuffling,… Continue reading
Problem : The java.util Collection classes are fail-fast, which means that if one thread changes a collection while another thread is traversing it through with an iterator the iterator.hasNext() or iterator.next() call will throw ConcurrentModificationException. Even the synchronized collection wrapper classes SynchronizedMap and SynchronizedList are only conditionally thread-safe, which means… Continue reading
An Iterator is a use once object to access the objects stored in a collection. Iterator design pattern (aka Cursor) is used, which is a behavioral design pattern that provides a way to access elements of a collection
SortedSet and SortedMap interfaces maintain sorted order. The classes, which implement the Comparable interface, impose natural order. By implementing Comparable, sorting an array of objects or a collection (List etc) is as simple as: Arrays.sort(myArray); Collections.sort(myCollection); // do not confuse “Collections” utility class with the // “Collection” interface without an… Continue reading
The key interfaces used by the collections framework are List, Set and Map. The List and Set extends the Collection interface. Should not confuse the Collection interface with the Collections class which is a utility class. Set (HashSet , TreeSet) List (ArrayList, LinkedList, Vector etc) A Set is a collection… Continue reading
Queue Stack First item to be inserted is the first one to be removed. Allows access to only last item inserted. This mechanism is called First In First Out (FIFO). An item is inserted or removed from one end called the “top” of the stack. This is called Last In… Continue reading
Vector / Hashtable ArrayList / HashMap Original classes before the introduction of Collections API. Vector & Hashtable are synchronized. Any method that touches their contents is thread-safe. So if you don’t need a thread safe collection, use the ArrayList or HashMap. Why pay the price of synchronization unnecessarily at the… Continue reading
Method Overloading Method Overriding Overloading deals with multiple methods in the same class with the same name but different method signatures. class MyClass { public void getInvestAmount(int rate) {…} public void getInvestAmount(int rate, long principal) { … } } Both the above methods have the same method names but different… Continue reading
The interfaces with no defined methods act like markers. They just tell the compiler that the objects of the classes implementing the interfaces with no defined methods need to be treated differently. Example java.io.Serializable, java.lang.Cloneable, java.util.EventListener etc. Marker interfaces are also known as “tag” interfaces since they tag all the… Continue reading
For polymorphic interface inheritance, where the client wants to only deal with a type and does not care about the actual implementation use interfaces. If you need to change your design frequently, you should prefer using interface to abstract. Coding to an interface reduces coupling and interface inheritance can achieve… Continue reading