StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

POJava: int array initializes with nonzero elements
primarykey
Id
12317668
data
AcceptedAnswerId
12375312
AnswerCount
2
ClosedDate
CommentCount
30
CommunityOwnedDate
CreationDate
2012-09-07T11:59:10.707
FavoriteCount
26
LastActivityDate
2012-10-05T15:08:37.157
LastEditDate
2012-09-10T12:53:37.573
LastEditorUserId
946635
OwnerUserId
946635
ParentId
0
PostTypeId
1
Score
130
ViewCount
6747
LastEditorDisplayName
text
Body
According to the JLS, an <code>int</code> array should be filled by zeros just after initialization. However, I am faced with a situation where it is not. Such a behavior occurs first in JDK 7u4 and also occurs in all later updates (I use 64-bit implementation). The following code throws exception: <pre><code>public static void main(String[] args) { int[] a; int n = 0; for (int i = 0; i < 100000000; ++i) { a = new int[10]; for (int f : a) if (f != 0) throw new RuntimeException("Array just after allocation: "+ Arrays.toString(a)); Arrays.fill(a, 0); for (int j = 0; j < a.length; ++j) a[j] = (n - j)*i; for (int f : a) n += f; } System.out.println(n); } </code></pre> The exception occurs after the JVM performs compilation of the code block and does not arise with <code>-Xint</code> flag. Additionally, the <code>Arrays.fill(...)</code> statement (as all other statements in this code) is necessary, and the exception does not occurs if it is absent. It is clear that this possible bug is bounded with some JVM optimization. Any ideas for the reason of such a behavior? Update: I see this behavior on HotSpot 64-bit server VM, Java version from 1.7.0_04 to 1.7.0_10 on Gentoo Linux, Debian Linux (both kernel 3.0 version) and MacOS Lion. This error can always be reproduced with the code above. I did not test this problem with a 32-bit JDK or on Windows. I already sent a bug report to the Oracle (bug id 7196857) and it will appear in public Oracle bug database in few days. Update: Oracle published this bug at their public bug database: <a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7196857" rel="noreferrer">http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7196857</a> 
Tags
<java><arrays><jvm><initialization><java-7>
Title
Java: int array initializes with nonzero elements
singulars
PostAcceptedAnswerId
1. PO
 singulars
 PostTypePostTypeId
 PTAnswer
PostParentId
1. This table or related slice is empty.
PostTypePostTypeId
1. PTQuestion
UserLastEditorUserId
1. USStanislav Poslavsky
UserOwnerUserId
1. USStanislav Poslavsky
plurals
PostLinksPostIdRelatedPostId
1. This table or related slice is empty.
PostLinksRelatedPostIdPostId
1. This table or related slice is empty.
PostsAcceptedAnswerId
1. This table or related slice is empty.
PostsParentIdCreationDate
1. PO
 singulars
 PostTypePostTypeId
 PTAnswer
2. PO
 singulars
 PostTypePostTypeId
 PTAnswer
VotesPostIdCreationDate
1. VO
 singulars
 PostPostId
 POJava: int array initializes with nonzero elements
 UserUserId
 This table or related slice is empty.
 VoteTypeVoteTypeId
 VTUpMod
2. VO
 singulars
 PostPostId
 POJava: int array initializes with nonzero elements
 UserUserId
 This table or related slice is empty.
 VoteTypeVoteTypeId
 VTUpMod
3. VO
 singulars
 PostPostId
 POJava: int array initializes with nonzero elements
 UserUserId
 This table or related slice is empty.
 VoteTypeVoteTypeId
 VTUpMod
CommentsPostId

Querying!

Guidance

A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.