polymorphism

来源： https://stackoverflow.com/questions/63742112/c-how-to-implement-polymorphic-object-creator-to-populate-a-table

来源： https://stackoverflow.com/questions/34886128/polymorphic-values-in-java

来源： https://stackoverflow.com/questions/34886128/polymorphic-values-in-java

来源： https://stackoverflow.com/questions/31608902/polymorphism-vs-strategy-pattern

来源： https://stackoverflow.com/questions/7754532/virtual-destructor-fail-using-array

问题 I'm fairly new to Java and would like to know how to accomplish the following task, and also, whether it is considered bad style, even if it is possible. Thank you. Fish f; // Fish is a superclass, Tuna t = new Tuna(); // to which Tuna is a subclass. f=t; // the Fish object "f" now refers to the Tuna object "t". // Both Fish and Tuna have an identical method (signature wise) called swim() , f.swim(); // and so Tuna's overridden swim() method is invoked here. But can I now get Fish's swim()

问题 I have a simple class hierarchy that I want to serialize using System.Text.Json. There are 3 classes. The base is Shape . Inherited ones are Box and Circle . I have a plan to use these classes as a tagged union on my frontend app so I just introduced a discriminator property Tag . I wrote a type convertor that supports serialization/deserialization of this hierarchy. What I'm trying to understand - is this a best approach to implement such functionality or not. Indeed the output result of

问题 Update: I modified the example so that can be compiled and tested. I have an implicit class that defines an enrichment method: case class Pipe[-I,+O,+R](f: I => (O, R)); object Pipe { // The problematic implicit class: implicit class PipeEnrich[I,O,R](val pipe: Pipe[I,O,R]) extends AnyVal { def >->[X](that: Pipe[O,X,R]): Pipe[I,X,R] = Pipe.fuse(pipe, that); def <-<[X](that: Pipe[X,I,R]): Pipe[X,O,R] = Pipe.fuse(that, pipe); } def fuse[I,O,X,R](i: Pipe[I,O,R], o: Pipe[O,X,R]): Pipe[I,X,R] =

问题 Update: I modified the example so that can be compiled and tested. I have an implicit class that defines an enrichment method: case class Pipe[-I,+O,+R](f: I => (O, R)); object Pipe { // The problematic implicit class: implicit class PipeEnrich[I,O,R](val pipe: Pipe[I,O,R]) extends AnyVal { def >->[X](that: Pipe[O,X,R]): Pipe[I,X,R] = Pipe.fuse(pipe, that); def <-<[X](that: Pipe[X,I,R]): Pipe[X,O,R] = Pipe.fuse(that, pipe); } def fuse[I,O,X,R](i: Pipe[I,O,R], o: Pipe[O,X,R]): Pipe[I,X,R] =

问题 I have MyClass and I want to call both mySubMethod(key) and mySubMethod2(key) for integer, but only call mySubMethod2(key) for non-integer. I tried below codes but doesn't work. I also tried to change K == int to something else, e.g. K == Integer , K.equals(int) and K.equals(Integer) etc., but all of them don't work. How Can I fix it? Thanks. public class MyClass<K,V> { public boolean myMethod(K key) { if (K == int) { mySubMethod(key); }else { // do nothing } mySubMethod2(key); return false;