java - 如何从匿名类中获取不同类型的数据

Question

我有一个对象将一些工作委托(delegate)给另一个正在实现接口(interface)的对象。然后，我正在创建实现此接口(interface)的匿名类，我想从中获取信息。

是否可以使用大小为 1 的最终数组作为指向基元的指针来与匿名类共享数据？

这是我的意思的一个工作示例:

public class ExampleClass
{
    public static final int INVALID_VALUE = -1;

    public static void main(final String[] args)
    {       
        final int[] buffer = { INVALID_VALUE }; // buffer is created
        final InterfaceA iaObject = new InterfaceA()
        {
            @Override
            public void doStuff(final String paramA)
            {
                buffer[0] = paramA.length(); // buffer is filled in anonymous class
            }
        };

        final ClassA objA = new ClassA(iaObject);
        objA.doStuff("hello, world");

        if (buffer[0] == INVALID_VALUE) // buffer is used
        {
            System.err.println("Invalid length !");
        }
        else
        {
            System.err.println("The length is : " + Integer.toString(buffer[0]));
        }
    }

    public static class ClassA
    {
        private final InterfaceA iaObject;

        public ClassA(final InterfaceA iaObject)
        {
            this.iaObject = iaObject;
        }

        public void doStuff(final String paramA)
        {
            this.iaObject.doStuff(paramA);
        }
    }

    public static interface InterfaceA
    {
        void doStuff(String paramA);
    }
}

谢谢

Answer 1

建议:为什么不对输出参数使用泛型？

interface InterfaceA {

   public <T> void doStuff( String paramA, Holder<T> holder );
}

class Holder<T> {

    public T t;
}

完整示例:

public class ExampleClass
{
   public static final int INVALID_VALUE = -1;

   public static void main(final String[] args)
   {       
      final InterfaceA< Integer > iaObject = new InterfaceA< Integer >() {
         @Override
         public Integer doStuff( String paramA, Holder<Integer> holder ) {
            return holder.value = paramA.length();
         }
      };

      final ClassA<Integer> objA = new ClassA<>( iaObject );
      int result = objA.doStuff("hello, world", new Holder<>( INVALID_VALUE ));
      if( result == INVALID_VALUE ) {
         System.err.println("Invalid length !");
      }
      else {
         System.err.println("The length is : " + Integer.toString( result ));
      }
   }

   public static class ClassA<T> {
      private final InterfaceA<T> iaObject;

      public ClassA( final InterfaceA<T> iaObject_ ) {
         this.iaObject = iaObject_;
      }

      public T doStuff( final String paramA, Holder<T> holder ) {
         return this.iaObject.doStuff( paramA, holder );
      }
   }

   public static interface InterfaceA<T> {
      public T doStuff( String paramA, Holder<T> resultHolder );
   }

   public static class Holder<T> {

      public T value;

      public Holder( T value_ ) {
         value = value_;
      }
   }
}