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Dec 14, 2012 · Thus, only the getter and setter are in the interface, whereas the field comes up in the implementation. And setNumber should return a void instead of int. For getting I suggest you to add int getNumber(). public interface MyInterface {. void setNumber(int num); // public is implicit in interfaces. int getNumber(); // obviously.
An interface has no state."; an interface has no state, but as far as an interface is concerned, public member variables are part of the object's public API. Unfortunately in Java-land, a public member variable is specifying something about the implementation of that API (namely that it's an in-memory variable) rather than leaving yourself the flexibility to change the implementation.
Jun 23, 2009 · 1) Fundamental difference between List and Set in Java is allowing duplicate elements. List in Java allows duplicates while Set doesn't allow any duplicate. If you insert duplicate in Set it will replace the older value. Any implementation of Set in Java will only contains unique elements.
May 25, 2012 · Set is just an interface. In order to retain order, you have to use a specific implementation of that interface and the sub-interface SortedSet, for example TreeSet or LinkedHashSet. You can wrap your Set this way: Set myOrderedSet = new LinkedHashSet(mySet); answered May 25, 2012 at 10:29. javatutorial.
thing.frob(); Each object, myObj and mySec, could be passed into this method, and this method could then use that object's frob method (assuming frob is part of the interface declaration). This is liberating. This allows you to do very powerful things, by programming to interfaces and not to implementations.
Feb 13, 2017 · Apart from that, in the Collection API, you can find the toArray methods, which are provided as a bridge between Collections and arrays. You can use this to convert your Collection to an array and iterate if you really need to: Object[] array = set.toArray(); for (Object element : array) {. System.out.println(element);
@MuhammedOzdogan , you can see item 22: "Use interfaces only to define types" of "Effective Java" : "The constant interface pattern is a poor use of interfaces. That a class uses some constants internally is an implementation detail. Implementing a constant interface causes this implementation detail to leak into the class’s exported API." –
Dec 17, 2012 · Checking the methods in class Set would answer your question. The main difference between set and list is that set do not respect the order. So if you add the items in a certain order, you are not garanteed to get them back in the same order. This is because Set optimizes the order to acheive the fastest access time possible.
May 29, 2016 · 12. Set is the general interface to a set-like collection, while HashSet is a specific implementation of the Set interface (which uses hash codes, hence the name). answered Feb 28, 2011 at 8:43. gmw. 437 3 15.
The most useful meaning for a "constructor in an interface", if allowed, would be if new Set<Fnord>() could be interpreted to mean "Give me something I can use as a Set<Fnord>"; if the author of Set<T> intended HashSet<T> to be the go-to implementation for things that didn't have a particular need for something else, the interface could then define new Set<Fnord>() could be considered synonymous with new HashSet<Fnord>().
