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https://issues.apache.org/jira/browse/HADOOP-15033?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16296844#comment-16296844
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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_r157764279
--- Diff:
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/Shell.java
---
@@ -89,6 +89,22 @@ public static boolean isJava7OrAbove() {
return true;
}
+ private static final boolean IS_JAVA9_OR_ABOVE;
+ static {
+ int major = 0;
+ try {
+ // 1.8.0 -> 1, 10-ea+30 -> 10, 18.03 -> 18, 11 -> 11 etc.
+ String version = System.getProperty("java.version");
+ major = Integer.parseInt(version.split("\\.")[0].split("-")[0]);
+ } catch (NumberFormatException ignored) {
+ }
+ IS_JAVA9_OR_ABOVE = major >= 9;
+ }
+
+ public static boolean isJava9OrAbove() {
+ return IS_JAVA9_OR_ABOVE;
+ }
--- End diff --
Yes, I had exactly the same in mind. Just haven't realized we may now
assume 8 as lowest version. Will it still be true if someone decides to
backport the fix to previous Hadoop versions?
> 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
>
>
> 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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