trying to fix graphhopper#283, Work around System.gc() calls for mobile

Author: Peter

core/src/main/java/com/graphhopper/storage/GHDirectory.java

@@ -150,7 +150,7 @@ public void clear()
             removeDA(da, da.getName(), false);
         }
         if (mmapDA != null)
-            mmapDA.cleanHack();
+            Helper.cleanHack();
         map.clear();
     }
 

core/src/main/java/com/graphhopper/storage/MMapDataAccess.java

@@ -135,7 +135,7 @@ protected boolean mapIt( long offset, long byteCount, boolean clearNew )
             {
                 newSegments = segmentsToMap;
                 clean(0, segments.size());
-                cleanHack();
+                Helper.cleanHack();
                 segments.clear();
             } else
             {
@@ -183,7 +183,7 @@ private ByteBuffer newByteBuffer( long offset, long byteCount ) throws IOExcepti
             {
                 ioex = tmpex;
                 trial++;
-                cleanHack();
+                Helper.cleanHack();
                 try
                 {
                     // mini sleep to let JVM do unmapping
@@ -293,13 +293,7 @@ void close( boolean forceClean )
         segments.clear();
         Helper.close(raFile);
         if (forceClean)
-            cleanHack();
-    }
-
-    void cleanHack()
-    {
-        // trying to force the release of the mapped ByteBuffer
-        System.gc();
+            Helper.cleanHack();
     }
 
     @Override
@@ -427,7 +421,7 @@ public void trimTo( long capacity )
         }
 
         clean(remainingSegNo, segments.size());
-        cleanHack();
+        Helper.cleanHack();
         segments = new ArrayList<ByteBuffer>(segments.subList(0, remainingSegNo));
 
         try
@@ -454,7 +448,7 @@ boolean releaseSegment( int segNumber )
 
         Helper.cleanMappedByteBuffer(segment);
         segments.set(segNumber, null);
-        cleanHack();
+        Helper.cleanHack();
         return true;
     }
 

core/src/main/java/com/graphhopper/util/Helper.java

@@ -405,6 +405,15 @@ public Object run() throws Exception
         }
     }
 
+    /**
+     * Trying to force the release of the mapped ByteBuffer. See
+     * http://stackoverflow.com/q/2972986/194609 and use only if you know what you are doing.
+     */
+    public static void cleanHack()
+    {
+        System.gc();
+    }
+
     public static String nf( long no )
     {
         // I like french localization the most: 123654 will be 123 654 instead