8003258: BufferedReader.lines()

Reviewed-by: alanb, mduigou, psandoz
Contributed-by: Brian Goetz <brian.goetz@oracle.com>, Henry Jen <henry.jen@oracle.com>

2 files changed, 158 insertions, 1 deletions

diff --git a/src/share/classes/java/io/BufferedReader.java b/src/share/classes/java/io/BufferedReader.java
index 556abb2a40..d742233a0f 100644
--- a/src/share/classes/java/io/BufferedReader.java
+++ b/src/share/classes/java/io/BufferedReader.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1996, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 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
@@ -26,6 +26,13 @@
 package java.io;
 
 
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+
 /**
  * Reads text from a character-input stream, buffering characters so as to
  * provide for the efficient reading of characters, arrays, and lines.
@@ -522,4 +529,64 @@ public class BufferedReader extends Reader {
             }
         }
     }
+
+    /**
+     * Returns a {@code Stream}, the elements of which are lines read from
+     * this {@code BufferedReader}.  The {@link Stream} is lazily populated,
+     * i.e, read only occurs during the
+     * <a href="../util/stream/package-summary.html#StreamOps">terminal
+     * stream operation</a>.
+     *
+     * <p> The reader must not be operated on during the execution of the
+     * terminal stream operation. Otherwise, the result of the terminal stream
+     * operation is undefined.
+     *
+     * <p> After execution of the terminal stream operation there are no
+     * guarantees that the reader will be at a specific position from which to
+     * read the next character or line.
+     *
+     * <p> If an {@link IOException} is thrown when accessing the underlying
+     * {@code BufferedReader}, it is wrapped in an {@link
+     * UncheckedIOException} which will be thrown from the {@code Stream}
+     * method that caused the read to take place. This method will return a
+     * Stream if invoked on a BufferedReader that is closed. Any operation on
+     * that stream requires reading from the BufferedReader after is it closed
+     * will cause an UncheckedIOException to be thrown.
+     *
+     * @return a {@code Stream<String>} providing the lines of text
+     *         described by this {@code BufferedReader}
+     *
+     * @since 1.8
+     */
+    public Stream<String> lines() {
+        Iterator<String> iter = new Iterator<String>() {
+            String nextLine = null;
+
+            @Override
+            public boolean hasNext() {
+                if (nextLine != null) {
+                    return true;
+                } else {
+                    try {
+                        nextLine = readLine();
+                        return (nextLine != null);
+                    } catch (IOException e) {
+                        throw new UncheckedIOException(e);
+                    }
+                }
+            }
+
+            @Override
+            public String next() {
+                if (nextLine != null || hasNext()) {
+                    String line = nextLine;
+                    nextLine = null;
+                    return line;
+                } else {
+                    throw new NoSuchElementException();
+                }
+            }
+        };
+        return StreamSupport.stream(Spliterators.spliteratorUnknownSize(iter, Spliterator.ORDERED));
+    }
 }
diff --git a/src/share/classes/java/io/UncheckedIOException.java b/src/share/classes/java/io/UncheckedIOException.java
new file mode 100644
index 0000000000..22c43e3807
--- /dev/null
+++ b/src/share/classes/java/io/UncheckedIOException.java
@@ -0,0 +1,90 @@
+/*
+ * Copyright (c) 2012, 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
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package java.io;
+
+import java.util.Objects;
+
+/**
+ * Wraps an {@link IOException} with an unchecked exception.
+ *
+ * @since   1.8
+ */
+public class UncheckedIOException extends RuntimeException {
+    private static final long serialVersionUID = -8134305061645241065L;
+
+    /**
+     * Constructs an instance of this class.
+     *
+     * @param   message
+     *          the detail message, can be null
+     * @param   cause
+     *          the {@code IOException}
+     *
+     * @throws  NullPointerException
+     *          if the cause is {@code null}
+     */
+    public UncheckedIOException(String message, IOException cause) {
+        super(message, Objects.requireNonNull(cause));
+    }
+
+    /**
+     * Constructs an instance of this class.
+     *
+     * @param   cause
+     *          the {@code IOException}
+     *
+     * @throws  NullPointerException
+     *          if the cause is {@code null}
+     */
+    public UncheckedIOException(IOException cause) {
+        super(Objects.requireNonNull(cause));
+    }
+
+    /**
+     * Returns the cause of this exception.
+     *
+     * @return  the {@code IOException} which is the cause of this exception.
+     */
+    @Override
+    public IOException getCause() {
+        return (IOException) super.getCause();
+    }
+
+    /**
+     * Called to read the object from a stream.
+     *
+     * @throws  InvalidObjectException
+     *          if the object is invalid or has a cause that is not
+     *          an {@code IOException}
+     */
+    private void readObject(ObjectInputStream s)
+        throws IOException, ClassNotFoundException
+    {
+        s.defaultReadObject();
+        Throwable cause = super.getCause();
+        if (!(cause instanceof IOException))
+            throw new InvalidObjectException("Cause must be an IOException");
+    }
+}