Add class to access WindowCache statistics

Change-Id: Iacb5b65539efd92a6b45afc307ebf246e8b8fccf
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/WindowCache.java

@@ -171,7 +171,10 @@ public class WindowCache {
 		return streamFileThreshold;
 	}
 
-	static WindowCache getInstance() {
+	/**
+	 * @return the cached instance.
+	 */
+	public static WindowCache getInstance() {
 		return cache;
 	}
 
@@ -269,11 +272,17 @@ public class WindowCache {
 			throw new IllegalArgumentException(JGitText.get().windowSizeMustBeLesserThanLimit);
 	}
 
-	int getOpenFiles() {
+	/**
+	 * @return the number of open files.
+	 */
+	public int getOpenFiles() {
 		return openFiles.get();
 	}
 
-	long getOpenBytes() {
+	/**
+	 * @return the number of open bytes.
+	 */
+	public long getOpenBytes() {
 		return openBytes.get();
 	}
 

org.eclipse.jgit/src/org/eclipse/jgit/storage/file/WindowCacheStats.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2018, David Pursehouse <david.pursehouse@gmail.com>
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.eclipse.jgit.storage.file;
+
+import org.eclipse.jgit.internal.storage.file.WindowCache;
+
+/**
+ * Accessor for stats about {@link WindowCache}.
+ *
+ * @since 4.11
+ *
+ */
+public class WindowCacheStats {
+	/**
+	 * @return the number of open files.
+	 */
+	public static int getOpenFiles() {
+		return WindowCache.getInstance().getOpenFiles();
+	}
+
+	/**
+	 * @return the number of open bytes.
+	 */
+	public static long getOpenBytes() {
+		return WindowCache.getInstance().getOpenBytes();
+	}
+}