问如何将java.lang.Appendable包装成java.io.Writer？

EN

import java.io.Closeable;
import java.io.Flushable;
import java.io.IOException;
import java.io.Writer;

public class AppendableWriterAdapter extends Writer {

      private Appendable appendable;

      public AppendableWriterAdapter(Appendable appendable) {
            this.appendable = appendable;
      }

      @Override
      public void write(char[] cbuf, int off, int len) throws IOException {
            appendable.append(String.valueOf(cbuf), off, len);
      }

      @Override
      public void flush() throws IOException {
            if (appendable instanceof Flushable) {
                  ((Flushable) appendable).flush();
            }
      }

      @Override
      public void close() throws IOException {
            flush();
            if (appendable instanceof Closeable) {
                  ((Closeable) appendable).close();
            }
      }

}

   import  java.io.Closeable;
   import  java.io.Flushable;
   import  java.io.IOException;
   import  java.io.Writer;
/**
   <P>{@code java NewWriterForAppendable}.</P>
 **/
public class NewWriterForAppendable  {
   /**
      <P>Demonstrates {@code newWriterForAppendable(apbl)} for creating a new {@code Writer} that wraps around {@code System.out} (writes to the console).</P>
    **/
   public static final void main(String[] igno_red)  {
      try  {
         NewWriterForAppendable.newWriterForAppendable(System.out).write("hello");
      }  catch(IOException iox)  {
         throw  new RuntimeException("WriterForAppendableXmpl", iox);
      }
   }
   /**
      <P>A {@code Flushable} whose {@code flush()} function does nothing. This is used by {@link #newWriterForAppendable(Appendable ap_bl) newWriterForAppendable}{@code (apbl)} as a (Java 1.5) delta.</P>

      @see  #newWriterForAppendable(Appendable) newWriterForAppendable(apbl)
    **/
   public static final Flushable FLUSHABLE_DO_NOTHING = new Flushable()  {
      public void flush()  {
      }
   };
   /**
      <P>A {@code Closeable} whose {@code close()} function does nothing. This is used by {@link #newWriterForAppendable(Appendable ap_bl) newWriterForAppendable}{@code (apbl)} as a (Java 1.5) delta.</P>

      @see  #newWriterForAppendable(Appendable) newWriterForAppendable(apbl)
    **/
   public static final Closeable CLOSEABLE_DO_NOTHING = new Closeable()  {
      public void close()  {
      }
   };
   /**
      <P>Creates a new {@code java.io.Writer} that wraps around a {@code java.lang.Appendable}. It properly {@link java.io.Writer#flush() flush}es and {@link java.io.Writer#close() close}s appendables that happened to also be {@link java.io.Flushable}s and/or {@link java.io.Closeable Closeable}s. This uses {@code instanceof} only in the constructor, and a delta in {@code flush()} and {@code close()}, which avoids having to use any logic or reflection after object construction.</P>

      <P>This function is released as a <A HREF="https://gist.github.com/aliteralmind/8494917">gist</A>, and is an example of the <A HREF="http://en.wikipedia.org/wiki/Adapter_pattern#Object_Adapter_pattern">Object Adapter pattern</A>. Thanks to <A HREF="http://stackoverflow.com/users/1211906/marc-baumbach">Marc Baumbach</A> on <A HREF="http://stackoverflow.com">{@code stackoverflow}</A> for the assistance. See (viewed 1/18/2014)
      <BR> &nbsp; &nbsp; <CODE><A HREF="http://stackoverflow.com/questions/21200421/how-to-wrap-a-java-lang-appendable-into-a-java-io-writer">http://stackoverflow.com/questions/21200421/how-to-wrap-a-java-lang-appendable-into-a-java-io-writer</A></CODE></P>

      @return  A new writer that uses an appendable to do its output.
      @see  #FLUSHABLE_DO_NOTHING
      @see  #CLOSEABLE_DO_NOTHING
    **/
   public static final Writer newWriterForAppendable(Appendable ap_bl)  {
      return  (new WFA(ap_bl));
   }
   private NewWriterForAppendable()  {
      throw  new IllegalStateException("constructor: Do not instantiate.");
   }
}
class WFA extends Writer  {
   private final Appendable apbl;
   private final Flushable  flbl;
   private final Closeable  clbl;
   public WFA(Appendable ap_bl)  {
      if(ap_bl == null)  {
         throw  new NullPointerException("ap_bl");
      }
      apbl = ap_bl;

      //Avoids instanceof at every call to flush() and close()
      flbl = (Flushable)((ap_bl instanceof Flushable) ? ap_bl
         :  NewWriterForAppendable.FLUSHABLE_DO_NOTHING);
      clbl = (Closeable)((ap_bl instanceof Closeable) ? ap_bl
         :  NewWriterForAppendable.CLOSEABLE_DO_NOTHING);
   }
   @Override
   public void write(char[] a_c, int i_ndexStart, int i_ndexEndX) throws IOException {
      apbl.append(String.valueOf(a_c), i_ndexStart, i_ndexEndX);
   }
   @Override
   public Writer append(char c_c) throws IOException {
      apbl.append(c_c);
      return  this;
   }
   @Override
   public Writer append(CharSequence c_q) throws IOException {
      apbl.append(c_q);
      return  this;
   }
   @Override
   public Writer append(CharSequence c_q, int i_ndexStart, int i_ndexEndX) throws IOException  {
      apbl.append(c_q, i_ndexStart, i_ndexEndX);
      return  this;
   }
   @Override
   public void flush() throws IOException {
      flbl.flush();
   }
   @Override
   public void close() throws IOException {
      flush();
      clbl.close();
   }

}