Java 参数化 class

Question

我尝试表示由状态组成的有限状态机。状态有一个转换列表，一个转换有一个开始状态和一个结束状态。在我的应用程序中，可以有几种类型的转换，它们都继承自抽象 class Transition.

我在 java 中有那些 class :

public class Etat<T extends Transition<T>> {
    private ObservableSet<T> listeTransitions;
}

public abstract class Transition<T extends Transition<T>> {
    private Etat<T> etatDepart;
    private Etat<T> etatArrivee;
}

我认为我有一个设计问题，因为单独设置“过渡”class 似乎很奇怪。有没有另一种方法可以做到并获得相同的结果？有人会有不同的做法吗？

感谢您的帮助:)

Answer 1

这是解决同一问题的另一种方法。请注意，关于不同类型的“转换”的详细信息不够多，因此我将一些 assumptions/left 部分空白。指出您希望我更改的内容。

此外，我更改了处理转换的方式。 Transitions 不是一个单独的对象，而是可以通过查看哪些 State 个对象被其他 State 个对象引用来找到。

import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

public class State
{

   public interface Transition
   {
   
      //put whatever methods/functionality/fields/etc that you like here.
   
   }

   public enum Type implements Transition
   {
   
      A,
      B,
      ;
      
      //If you add any methods to the interface, be sure to implement them in all values of this enum (or give a default/abstract implementation for them to use)
   
   }
   
   private final int id;
   private final Map<State, Type> inboundTransitions = new HashMap<>();
   private final Map<State, Type> outboundTransitions = new HashMap<>();
   
   public State(int id)
   {
   
      this.id = id;
   
   }

   public int id()
   {
   
      return this.id;
   
   }
   
   public Map<State, Type> inboundTransitions()
   {
   
      return Collections.unmodifiableMap(this.inboundTransitions);
   
   }
      
   public Map<State, Type> outboundTransitions()
   {
   
      return Collections.unmodifiableMap(this.outboundTransitions);
   
   }
      
   public static void addTransition(State startingState, State endingState, Type transitionType)
   {
   
      startingState.outboundTransitions.put(endingState, transitionType);
      endingState.inboundTransitions.put(startingState, transitionType);
   
   }
   
   public static void main(String[] args)
   {
   
      //now, to show how this would be used, using your image as an example.
   
      State s0 = new State(0);
      State s1 = new State(1);
      State s2 = new State(2);
      State s3 = new State(3);
      
      State.addTransition(s0, s1, Type.B); // s0 ---b---> s1
      State.addTransition(s0, s2, Type.A); // s0 ---a---> s2
      State.addTransition(s1, s3, Type.A); // s1 ---a---> s3
      State.addTransition(s2, s3, Type.A); // s2 ---a---> s3
   
   }

}

如果您使用的是 Java 14 或更高版本，您可以使用 Records 来保持简短。

import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

public record State(int id, Map<State, Type> inboundTransitions, Map<State, Type> outboundTransitions)
{

   public interface Transition
   {
   
      //put whatever methods/functionality/fields/etc that you like here.
   
   }

   public enum Type implements Transition
   {
   
      A,
      B,
      ;
      
      //If you add any methods to the interface, be sure to implement them in all values of this enum (or give a default/abstract implementation for them to use)
   
   }
   
   public static void addTransition(State startingState, State endingState, Type transitionType)
   {
   
      startingState.outboundTransitions.put(endingState, transitionType);
      endingState.inboundTransitions.put(startingState, transitionType);
   
   }
   
   public static void main(String[] args)
   {
   
      //now, to show how this would be used, using your image as an example.
   
      State s0 = new State(0, new HashMap<>(), new HashMap<>());
      State s1 = new State(1, new HashMap<>(), new HashMap<>());
      State s2 = new State(2, new HashMap<>(), new HashMap<>());
      State s3 = new State(3, new HashMap<>(), new HashMap<>());
      
      State.addTransition(s0, s1, Type.B); // s0 ---b---> s1
      State.addTransition(s0, s2, Type.A); // s0 ---a---> s2
      State.addTransition(s1, s3, Type.A); // s1 ---a---> s3
      State.addTransition(s2, s3, Type.A); // s2 ---a---> s3
   
   }

}

Java 参数化 class

Java parameterized class

java

generics

parameterized