ant and java 8 - “major version 52 is newer than 51, the highest major version supported by this compiler”

Question

I am trying to upgrade my ant project from java 7 to java 8.
(the project deployed in \"Eclipse Kepler\" with \"Java™ 8 support to Eclipse Kepler SR2\")

For that

Answer 1

In Ubuntu, I simply fixed it by configure javah from jdk(either openjdk or oracle jdk works) 7 to 8:

$ javah -classpath . -d jni/ NativeSorting
./NativeSorting.class: major version 52 is newer than 51, the highest major version supported by this compiler.
  It is recommended that the compiler be upgraded.
$ sudo update-alternatives --config javah
There are 4 choices for the alternative javah (providing /usr/bin/javah).

  Selection    Path                                         Priority   Status
------------------------------------------------------------
  0            /usr/lib/jvm/java-8-openjdk-amd64/bin/javah   1081      auto mode
* 1            /usr/lib/jvm/java-7-openjdk-amd64/bin/javah   1071      manual mode
  2            /usr/lib/jvm/java-8-openjdk-amd64/bin/javah   1081      manual mode
  3            /usr/lib/jvm/jdk1.7.0_80/bin/javah            1000      manual mode
  4            /usr/lib/jvm/jdk1.8.0_131/bin/javah           1000      manual mode

Press  to keep the current choice[*], or type selection number: 2
update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/bin/javah to provide /usr/bin/javah (javah) in manual mode
$ javah -classpath . -d jni/ NativeSorting
$