Java静态arraylist初始化问题

Question

This issue happens to me only in production and am myself not able to reproduce it during testing/development

I have a class containing lot of static variables.

public class MyClass {

 private static final ArrayList<String> MY_LIST = new ArrayList<String>(Arrays.asList("DCNC", "DJPC", "DKRC", "DTHC", "DTWC", "DILC", "DALC", "DSEC", "DTRC", "DZAC", "DARC", "DCOC", "DRUC", "DMYC", "DMXC", "DPKC", "DIDC", "DBRC", "DNPC", "DJOC", "DLKC", "DVNC", "DKHC", "DLAC"));
 public static final HashMap<String, ArrayList<String>> MY_MAP = new HashMap<String, ArrayList<String>>();

 static {
     MY_MAP.put("test1", MY_LIST);
     MY_MAP.put("test2", MY_LIST);
     MY_MAP.put("test3", MY_LIST);
     MY_MAP.put("test4", MY_LIST);
     MY_MAP.put("test5", MY_LIST);
     MY_MAP.put("test6", MY_LIST);

 }

 private static final ArrayList<String> MY_SECOND_LIST = new ArrayList<String>(Arrays.asList("DCNC", "DJPC", "DKRC", "DTHC", "DTWC", "DILC", "DALC", "DSEC", "DTRC", "DZAC", "DARC", "DCOC", "DRUC", "DMYC", "DMXC", "DPKC", "DIDC", "DBRC", "DNPC", "DJOC", "DLKC", "DVNC", "DKHC", "DLAC"));
 private static final ArrayList<String> MY_THIRD_LIST = new ArrayList<String>(Arrays.asList("DJPC", "DKRC", "DTHC", "DTWC", "DILC", "DALC", "DSEC", "DTRC", "DZAC", "DARC", "DCOC", "DRUC", "DMYC", "DMXC", "DPKC", "DIDC", "DBRC", "DNPC", "DJOC", "DLKC", "DVNC", "DKHC", "DLAC"));
 private static final ArrayList<String> MY_FOURTH_LIST = new ArrayList<String>(Arrays.asList("DCNC", "DKRC", "DTHC", "DTWC", "DILC", "DALC", "DSEC", "DTRC", "DZAC", "DARC", "DCOC", "DRUC", "DMYC", "DMXC", "DPKC", "DIDC", "DBRC", "DNPC", "DJOC", "DLKC", "DVNC", "DKHC", "DLAC"));
 private static final ArrayList<String> MY_FIFTH_LIST = new ArrayList<String>(Arrays.asList("DKRC", "DTHC", "DTWC", "DILC", "DALC", "DSEC", "DTRC", "DZAC", "DARC", "DCOC", "DRUC", "DMYC", "DMXC", "DPKC", "DIDC", "DBRC", "DNPC", "DJOC", "DLKC", "DVNC", "DKHC", "DLAC"));

 public static final HashMap<String, ArrayList<String>> MY_SECOND_MAP = new HashMap<String, ArrayList<String>>();

 static {
     MY_SECOND_MAP.put("T1", MY_SECOND_LIST);
     MY_SECOND_MAP.put("T2", MY_THIRD_LIST);
     MY_SECOND_MAP.put("T3", MY_FOURTH_LIST);
     MY_SECOND_MAP.put("T4", MY_FIFTH_LIST);
 }     

}

When I access MY_MAP.get("test1") or MY_MAP.get("test2") or for that matter on any key on MY_MAP , I always get empty list. Looks like for some reason MY_LIST is initialized to empty list.

Can anyone tell in what rare case can this happen? This is constantly happening in production environment but am not able to reproduce this locally.

Environment details:

• Redhat Enterprise 5.3 Server 64-bit (Update U3)
• JDK7
• jvm options

--FLApplication.machineProtocol=UDP -Dclient.encoding.override=UTF-8 -Dfile.encoding=UTF-8 -Xmx512m -Xms512m -XX:SurvivorRatio=8 -XX:PermSize=128M -XX:MaxPermSize=128M -XX:+CMSClassUnloadingEnabled -XX:+CMSPermGenSweepingEnabled

Answer 1

Posting on behalf of @Marko Topolnik and @marco13 It was what @Marko Topolnik suggested in one of his comments. There was indeed a removeAll statement which was reachable only in production which was actually emptying the list.

As @marco13 suggested, this issue would have been identified if only we created unmodifiable lists at the first place. So to avoid bumping into such issues, the code could be modified like below

     private static final List<String> MY_LIST = Collections.unmodifiableList(Arrays.asList("DCNC", "DJPC", "DKRC", "DTHC", "DTWC", "DILC", "DALC", "DSEC", "DTRC", "DZAC", "DARC", "DCOC", "DRUC", "DMYC", "DMXC", "DPKC", "DIDC", "DBRC", "DNPC", "DJOC", "DLKC", "DVNC", "DKHC", "DLAC"));