added lines() in LineReader

guava-tests/test/com/google/common/io/LineBufferTest.java

@@ -26,6 +26,8 @@
 import java.nio.CharBuffer;
 import java.util.Arrays;
 import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 /**
  * Unit tests for {@link LineBuffer} and {@link LineReader}.
@@ -74,6 +76,10 @@ public String apply(String value) {
       assertEquals(expectRead, readUsingJava(input, chunk));
       assertEquals(expectRead, readUsingReader(input, chunk, true));
       assertEquals(expectRead, readUsingReader(input, chunk, false));
+      assertTrue(expectRead.containsAll(readUsingReaderGetLines(input, chunk, true)
+          .collect(Collectors.toList())));
+      assertTrue(expectRead.containsAll(readUsingReaderGetLines(input, chunk, false)
+          .collect(Collectors.toList())));
     }
   }
 
@@ -121,6 +127,13 @@ private static List<String> readUsingReader(String input, int chunk, boolean asR
     return lines;
   }
 
+  private static Stream<String> readUsingReaderGetLines(String input, int chunk, boolean asReader) {
+      Readable readable =
+          asReader ? getChunkedReader(input, chunk) : getChunkedReadable(input, chunk);
+      LineReader r = new LineReader(readable);
+      return r.lines();
+    }
+
   // Returns a Readable that is *not* a Reader.
   private static Readable getChunkedReadable(String input, int chunk) {
     final Reader reader = getChunkedReader(input, chunk);

guava/src/com/google/common/io/LineReader.java

@@ -14,19 +14,29 @@
 
 package com.google.common.io;
 
-import static com.google.common.base.Preconditions.checkNotNull;
-import static com.google.common.io.CharStreams.createBuffer;
-
-import com.google.common.annotations.Beta;
-import com.google.common.annotations.GwtIncompatible;
-import com.google.errorprone.annotations.CanIgnoreReturnValue;
 import java.io.IOException;
 import java.io.Reader;
+import java.io.UncheckedIOException;
 import java.nio.CharBuffer;
 import java.util.ArrayDeque;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import java.util.Optional;
 import java.util.Queue;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+
 import javax.annotation.CheckForNull;
 
+import com.google.common.annotations.Beta;
+import com.google.common.annotations.GwtIncompatible;
+import com.google.errorprone.annotations.CanIgnoreReturnValue;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+import static com.google.common.io.CharStreams.createBuffer;
+
 /**
  * A class for reading lines of text. Provides the same functionality as {@link
  * java.io.BufferedReader#readLine()} but for all {@link Readable} objects, not just instances of
@@ -84,4 +94,43 @@ public String readLine() throws IOException {
     }
     return lines.poll();
   }
+
+    /**
+     * Returns a {@code Stream}, the elements of which are lines read from
+     * this {@code LineReader}.
+     *
+     * @return a {@code Stream<String>} providing the lines of text
+     *         described by this {@code LineReader}
+     */
+    public Stream<String> lines()
+    {
+        Iterator<String> iterator = new Iterator<String>() {
+            String nextLine = "";
+            @Override
+            public boolean hasNext() {
+                if (!nextLine.equals("")) {
+                    return true;
+                } else {
+                    try {
+                        nextLine = Optional.ofNullable(readLine()).orElse("");
+                        return (!nextLine.equals(""));
+                    } catch (IOException e) {
+                        throw new UncheckedIOException(e);
+                    }
+                }
+            }
+            @Override
+            public String next() {
+                if (!nextLine.equals("") || hasNext()) {
+                    String line = nextLine;
+                    nextLine = "";
+                    return line;
+                } else {
+                    throw new NoSuchElementException();
+                }
+            }
+        };
+        return StreamSupport.stream(Spliterators.spliteratorUnknownSize(
+            iterator, Spliterator.ORDERED | Spliterator.NONNULL), false);
+    }
 }