Question

Hey Guys我对Java很新，我在使用泛型方面有点挣扎。基本上我想迭代存储在Set-class中的转换集合。如果我创建一个Set类的实例我没有遇到任何问题，但我想迭代存储在FA类中的转换，这会导致一些麻烦（无法将Object转换为Transition）。必须有一些问题与代码，但我无法找到它:(

public static void main(String[] args) {

    FA fa = new FA( new Set<String>("A", "B", "C"),
                     "A", 
                     new Set<Transition>(new Transition("A", 1, "B"),
                                        new Transition( "B",2,"C")),
                                        new Set<String>("C") );

    Set<Transition> t=new Set();
    t.add(new Transition("A", 1, "B"));

    for (Transition transition : t) {   
        //Works as intended
    }

   //error cannot convert Object to Transition
    for (Transition transition : fa.Transitions) {  
        //not working
    }

FA级：

public class FA<T>
{
    public Set<T>         States;
    public T            StartState;
    public Set<Transition>         Transitions;
    public Set<T>         FinalState;

    public FA(){}

    public FA( Set<T> states, T startstate, Set<Transition> transitions, Set<T> finalstate) {

      States     = states;
      StartState = startstate;
      Transitions= transitions; 
      FinalState = finalstate ;
    }
}

设置级：

 public class Set<T> implements Iterable<T>
 {

  private ArrayList<T> Menge=new ArrayList<T>(); 

  public Set( T ... menge ) {   
    for( int i=0; i < menge.length; i++ ) {     
        Menge.add((T) menge[i] );
    }
  }

public int count() {
    return Menge.size();
}

public T get(int i) {
    return (T)Menge.get(i);
}

public void add(T i) {
            Menge.add((T)i);

}

@Override
public String toString() {
    return Menge.toString();
}

@Override
public Iterator<T> iterator() {
    // TODO Auto-generated method stub
    return Menge.iterator();
 }
}

过渡级：

 public class Transition<T>
 {
  private T  Source;
  private T Label;
  private T  Target;

 public Transition( T source, T label, T target ) {
    Source = source;
    Label  = label ;
    Target = target;
 }

 public T get(int i)
 {
    if(i==1)return Source;
    if(i==2)return Label;
    return Source;
 }

 @Override
 public String toString() {
    return Source.toString() + " - " + Label.toString() + " -> " + Target.toString();
 }
}

Answer 1

fa的声明是错误的，它应该是：

FA<Transition> fa = new FA<>( new Set<String>("A", "B", "C"),
                     "A", 
                     new Set<Transition>(new Transition("A", 1, "B"),
                                        new Transition( "B",2,"C")),
                                        new Set<String>("C") );

顺便说一下，在通用实例化中还有一些其他错误，我建议你阅读http://docs.oracle.com/javase/tutorial/java/generics/

Java迭代泛型

1 个答案: