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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-15033) Use java.util.zip.CRC32C for Java 9 and above
Date Wed, 10 Jan 2018 11:45:01 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-15033?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16320121#comment-16320121
] 

ASF GitHub Bot commented on HADOOP-15033:
-----------------------------------------

Github user dchuyko commented on a diff in the pull request:

    https://github.com/apache/hadoop/pull/291#discussion_r160654155
  
    --- Diff: hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/Shell.java
---
    @@ -86,7 +86,15 @@
        */
       @Deprecated
       public static boolean isJava7OrAbove() {
    -    return true;
    +    return isJavaSpecAtLeast(7);
    +  }
    +
    +  // "1.8"->8, "9"->9, "10"->10
    +  private static final int JAVA_SPEC_VER = Math.max(8, Integer.parseInt(
    +      System.getProperty("java.specification.version").split("\\.")[0]));
    +
    +  public static boolean isJavaSpecAtLeast(int version) {
    --- End diff --
    
    Done all 3.


> Use java.util.zip.CRC32C for Java 9 and above
> ---------------------------------------------
>
>                 Key: HADOOP-15033
>                 URL: https://issues.apache.org/jira/browse/HADOOP-15033
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: performance, util
>    Affects Versions: 3.0.0
>            Reporter: Dmitry Chuyko
>              Labels: Java9, common, jdk9
>         Attachments: HADOOP-15033.001.patch, HADOOP-15033.001.patch, HADOOP-15033.002.patch,
HADOOP-15033.003.patch, HADOOP-15033.003.patch, HADOOP-15033.004.patch, HADOOP-15033.005.diff,
HADOOP-15033.005.diff, HADOOP-15033.005.diff, HADOOP-15033.005.patch, HADOOP-15033.006.patch,
HADOOP-15033.007.patch, HADOOP-15033.007.patch, HADOOP-15033.008.patch, HADOOP-15033.009.patch,
HADOOP-15033.009.patch, HADOOP-15033.009.patch, HADOOP-15033.009.patch, HADOOP-15033.009.patch,
HADOOP-15033.009.patch, HADOOP-15033.009.patch
>
>
> java.util.zip.CRC32C implementation is available since Java 9.
> https://docs.oracle.com/javase/9/docs/api/java/util/zip/CRC32C.html
> Platform specific assembler intrinsics make it more effective than any pure Java implementation.
> Hadoop is compiled against Java 8 but class constructor may be accessible with method
handle on 9 to instances implementing Checksum in runtime.



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