override read(), leads to ~10 percent performance increase

src/checkstyle/com/puppycrawl/tools/checkstyle/StringArrayReader.java

@@ -24,7 +24,11 @@ import java.io.IOException;
 /**
  * A Reader that reads from an underlying String array, assuming each
  * array element corresponds to one line of text.
- *
+ * <p>
+ * <strong>Note: This class is not thread safe, concurrent reads might produce
+ * unexpected results!</strong> Checkstyle only works with one thread so
+ * currently there is no need to introduce synchronization here.
+ * </p>
  * @author <a href="mailto:lkuehne@users.sourceforge.net">Lars Kühne</a>
  */
 class StringArrayReader extends Reader
@@ -71,9 +75,7 @@ class StringArrayReader extends Reader
     /** @see Reader */
     public int read(char[] aCbuf, int aOff, int aLen) throws IOException
     {
-        if (mClosed) {
-            throw new IOException("already closed");
-        }
+        ensureOpen();
 
         int retVal = 0;
 
@@ -105,4 +107,37 @@ class StringArrayReader extends Reader
         }
         return retVal;
     }
+
+    /** @see Reader */
+    public int read() throws IOException
+    {
+        if (mUnreportedNewline) {
+            mUnreportedNewline = false;
+            return '\n';
+        }
+
+        if (mArrayIdx < mUnderlyingArray.length
+            && mStringIdx < mUnderlyingArray[mArrayIdx].length() )
+        {
+            // this is the common case,
+            // avoid char[] creation in super.read for performance
+            ensureOpen();
+            return mUnderlyingArray[mArrayIdx].charAt(mStringIdx++);
+        }
+        else {
+            // don't bother duplicating the new line handling above
+            // for the uncommon case
+            return super.read();
+        }
+    }
+
+    /** Throws an IOException if the reader has already been closed. */
+    private void ensureOpen() throws IOException
+    {
+        if (mClosed) {
+            throw new IOException("already closed");
+        }
+    }
+
+
 }

src/tests/com/puppycrawl/tools/checkstyle/StringArrayReaderTest.java

@@ -12,7 +12,7 @@ public class StringArrayReaderTest
         super(name);
     }
 
-    public void testMisc()
+    public void testClose()
     {
         final StringArrayReader o = new StringArrayReader(new String[] {""});
         assertNotNull(o);
@@ -24,4 +24,25 @@ public class StringArrayReaderTest
         catch (IOException e) {
         }
     }
+
+    public void testLineBreakSingleChar()
+    {
+        final StringArrayReader o = new StringArrayReader(new String[] {"a", "bc"});
+        try {
+            int a = o.read();
+            assertEquals('a', a);
+            int nl1 = o.read();
+            assertEquals('\n', nl1);
+            int b = o.read();
+            assertEquals('b', b);
+            int c = o.read();
+            assertEquals('c', c);
+            int nl2 = o.read();
+            assertEquals('\n', nl2);
+            int eof = o.read();
+            assertEquals(-1, eof);
+        }
+        catch (IOException ex) {
+        }
+    }
 }