A DESCRIPTION OF THE FIX :
javac DefaultFileManager.Archive retains excessive memory for Zip entry names

For each additional entry within a "directory" of a zip/jar, the current implementation retains a List, a String and a long char[]. The char[] is longer than necessary because the String created by String.substring contains the entire path name, As well as increasing the amount of memory necessary, the extra objects may impact GC performance for longer lived processes.

The patch replaces the oversized String with a trimmed char[]. The custom linked List implementation is replaced by a standard ArrayList. So for each additional entry we have one short char[] and one or two extra elements in the ArrayList array.

The patch does increase start up times marginally because of the extra copying. However, javac becomes more likely to complete.

As an example, without the patch the following command gives an OutOfMemoryError dump (assuming the mustang source is in the specified directory).

javac -d scratch/  $( find ~/mustang/current/j2se/src/share/classes/java/ -name "*.java" -print | grep --invert-match --regexp=- )



--- /home/tackline/mustang/current/j2se/src/share/classes/com/sun/tools/javac/util/DefaultFileManager.java      2006-05-26 12:01:51.000000000 +0100
+++ java/com/sun/tools/javac/util/DefaultFileManager.java       2006-05-27 12:47:51.000000000 +0100
@@ -269,10 +269,10 @@
                 subdirectory = subdirectory.replace('\\', '/');
                 if (!subdirectory.endsWith("/")) subdirectory = subdirectory + "/";
             }
-            List<String> files = archive.map.get(subdirectory);
+            ArrayList<char[]> files = archive.map.get(subdirectory);
             if (files != null) {
-                for (String file; !files.isEmpty(); files = files.tail) {
-                    file = files.head;
+                for (char[] fileChars : files) {
+                    String file = String.valueOf(fileChars);
                     if (isValidFile(file, fileKinds)) {
                         ZipEntry ze = archive.zdir.getEntry(subdirectory + file);
                         JavaFileObject fe = new ZipFileObject(file, archive.zdir, ze);
@@ -376,9 +376,9 @@
      * mapping directory names to lists of files (basenames).
      */
     public static class Archive {
-        final Map<String,List<String>> map;
+        final Map<String,ArrayList<char[]>> map;
         final public ZipFile zdir;
-        public Archive(ZipFile zdir, Map<String,List<String>> map) {
+        public Archive(ZipFile zdir, Map<String,ArrayList<char[]>> map) {
             this.zdir = zdir;
             this.map = map;
         }
@@ -389,8 +389,16 @@
             String basename = name.substring(i+1);
             if (basename.length() == 0)
                 return false;
-            List<String> list = map.get(dirname);
-            return (list != null && list.contains(basename));
+            ArrayList<char[]> list = map.get(dirname);
+            if (list == null)
+                return false;
+            char[] basenameChars = basename.toCharArray();
+            for (char[] candidate : list) {
+                if (java.util.Arrays.equals(basenameChars, candidate)) {
+                    return true;
+                }
+            }
+            return false;
         }
     }
     public static class MissingArchive extends Archive {
@@ -422,8 +430,8 @@
                 return archive;
             }

-            final Map<String,List<String>> map
-                = new HashMap<String,List<String>>();
+            final Map<String,ArrayList<char[]>> map
+                = new HashMap<String,ArrayList<char[]>>();

             for (java.util.Enumeration<? extends ZipEntry> e = zdir.entries();
                  e.hasMoreElements();) {
@@ -431,14 +439,15 @@
                 String name = entry.getName();
                 int i = name.lastIndexOf('/');
                 String dirname = name.substring(0, i+1);
-                String basename = name.substring(i+1);
-                if (basename.length() == 0)
+                char[] basename = name.substring(i+1).toCharArray();
+                if (basename.length == 0)
                     continue;
-                List<String> list = map.get(dirname);
-                if (list == null)
-                    list = List.nil();
-                list = list.prepend(basename);
-                map.put(dirname, list);
+                ArrayList<char[]> list = map.get(dirname);
+                if (list == null) {
+                    list = new ArrayList<char[]>();
+                    map.put(new String(dirname), list);
+                }
+                list.add(basename);
             }

             archive = new Archive(zdir, map);