src/java.base/share/classes/java/lang/Readable.java

*** 1,7 ****
  /*
!  * Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
--- 1,7 ----
  /*
!  * Copyright (c) 2003, 2017, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
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--- 24,35 ----
   */
  
  package java.lang;
  
  import java.io.IOException;
+ import java.nio.CharBuffer;
+ import java.util.Objects;
  
  /**
   * A {@code Readable} is a source of characters. Characters from
   * a {@code Readable} are made available to callers of the read
   * method via a {@link java.nio.CharBuffer CharBuffer}.
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       * @throws IOException if an I/O error occurs
       * @throws NullPointerException if cb is null
       * @throws java.nio.ReadOnlyBufferException if cb is a read only buffer
       */
      public int read(java.nio.CharBuffer cb) throws IOException;
+ 
+     /**
+      * Reads all characters from this source and writes the characters to
+      * the given appendable in the order that they are read. On return, the
+      * source of characters will be at its end.
+      * <p>
+      * This method may block indefinitely reading from the readable, or
+      * writing to the appendable. Where this source or the appendable is
+      * {@link AutoCloseable closeable}, then the behavior when either are
+      * <i>asynchronously closed</i>, or the thread interrupted during the transfer,
+      * is highly readable and appendable specific, and therefore not specified.
+      * <p>
+      * If an I/O error occurs reading from the readable or writing to the
+      * appendable, then it may do so after some characters have been read or
+      * written. Consequently the readable may not be at end of its data and
+      * one, or both participants may be in an inconsistent state. That in mind
+      * all additional measures required by one or both participants in order to
+      * eventually free their internal resources have to be taken by the caller
+      * of this method.
+      *
+      * @param  out the appendable, non-null
+      * @return the number of characters transferred
+      * @throws IOException if an I/O error occurs when reading or writing
+      * @throws NullPointerException if {@code out} is {@code null}
+      *
+      * @since 10
+      */
+     public default long transferTo(Appendable out) throws IOException {
+         Objects.requireNonNull(out, "out");
+         long transferred = 0;
+         CharBuffer buffer = CharBuffer.allocate(8192);
+         int read;
+         while ((read = this.read(buffer)) >= 0) {
+             buffer.rewind();
+             out.append(buffer, 0, read);
+             transferred += read;
+         }
+         return transferred;
+     }
  }