# Java 7 compatibility issues

**URL:** <https://community.konduit.ai/t/java-7-compatibility-issues/306>\
**Category:** ND4J\
**Created:** [March 23, 2020, 1:42pm UTC](https://community.konduit.ai/t/java-7-compatibility-issues/306 "2020-03-23T13:42:38Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![mheck136](https://yyz1.discourse-cdn.com/flex035/user_avatar/community.konduit.ai/mheck136/32/106_2.png) [@mheck136](https://community.konduit.ai/u/mheck136)\
**Post date:** [March 23, 2020, 1:42pm UTC](https://community.konduit.ai/t/java-7-compatibility-issues/306/1 "2020-03-23T13:42:38Z")

</div>

Hi there, I’m trying to integrate nd4j into an application running on a quite old tech stack including java 7. When running a really simple piece of code, I get an error regarding the class version:

```
java.lang.UnsupportedClassVersionError: org/nd4j/linalg/cpu/nativecpu/CpuBackend : Unsupported major.minor version 52.0

```

The [nd4j getting started guide](https://nd4j.org/getstarted) states that jdk 1.7 is the minimum version, but the error states that the class has been compiled using java 8.  
Is this a bug or is the getting started guide not up to date with the minimal requirements of nd4j?

Thanks,  
Martin

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<div class="post-metadata">

**Author:** ![treo](https://yyz1.discourse-cdn.com/flex035/user_avatar/community.konduit.ai/treo/32/47_2.png) [@treo](https://community.konduit.ai/u/treo)\
**Post date:** [March 23, 2020, 2:34pm UTC](https://community.konduit.ai/t/java-7-compatibility-issues/306/2 "2020-03-23T14:34:13Z")

</div>

For the most part it should still be compatible with Java 7. What part is it that throws this error?

---

<div class="post-metadata">

**Author:** ![mheck136](https://yyz1.discourse-cdn.com/flex035/user_avatar/community.konduit.ai/mheck136/32/106_2.png) [@mheck136](https://community.konduit.ai/u/mheck136)\
**Post date:** [March 24, 2020, 8:17am UTC](https://community.konduit.ai/t/java-7-compatibility-issues/306/3 "2020-03-24T08:17:46Z")

</div>

It’s a simple UnitTest I’ve write to confirm that nd4j has been loaded correctly by just invoking a method:

```
import org.nd4j.linalg.api.ndarray.INDArray;
import org.nd4j.linalg.factory.Nd4j;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.testng.annotations.Test;

import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.is;
import static org.hamcrest.Matchers.notNullValue;

public class Nd4jTest {

    private static final Logger LOGGER = LoggerFactory.getLogger(Nd4jTest.class);

    @Test
    public void testJd4jIsPresent() {
        INDArray x = Nd4j.zeros(3,4);
        assertThat(x, is(notNullValue()));
    }

}

```

When running on java 8, the test succeeds, but on java 7, I get the error I mentioned in my first post:

```
java.lang.UnsupportedClassVersionError: org/nd4j/linalg/cpu/nativecpu/CpuBackend : Unsupported major.minor version 52.0

at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:278)
at java.util.ServiceLoader$LazyIterator.next(ServiceLoader.java:363)
at java.util.ServiceLoader$1.next(ServiceLoader.java:445)
at org.nd4j.linalg.factory.Nd4jBackend.load(Nd4jBackend.java:162)
at org.nd4j.linalg.factory.Nd4j.initContext(Nd4j.java:5128)
at org.nd4j.linalg.factory.Nd4j.<clinit>(Nd4j.java:226)
at com.example.Nd4jTest.testJd4jIsPresent(Nd4jTest.java:19)

```

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<div class="post-metadata">

**Author:** ![treo](https://yyz1.discourse-cdn.com/flex035/user_avatar/community.konduit.ai/treo/32/47_2.png) [@treo](https://community.konduit.ai/u/treo)\
**Post date:** [March 24, 2020, 10:04am UTC](https://community.konduit.ai/t/java-7-compatibility-issues/306/4 "2020-03-24T10:04:58Z")

</div>

You are right, for some reason the default target has been java 8 ever since the beta4 release. However, that change wasn’t fully intentional.

There are a few modules that intentionally require java 8 and up, but that shouldn’t apply to the core modules.

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<div class="post-metadata">

**Author:** ![mheck136](https://yyz1.discourse-cdn.com/flex035/user_avatar/community.konduit.ai/mheck136/32/106_2.png) [@mheck136](https://community.konduit.ai/u/mheck136)\
**Post date:** [March 24, 2020, 12:03pm UTC](https://community.konduit.ai/t/java-7-compatibility-issues/306/5 "2020-03-24T12:03:22Z")

</div>

Thanks for having a look!

Is it possible to move the target language level back to java 7 where possible and integrate this in the next release? Should I create an issue on GitHub for this?

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<div class="post-metadata">

**Author:** ![treo](https://yyz1.discourse-cdn.com/flex035/user_avatar/community.konduit.ai/treo/32/47_2.png) [@treo](https://community.konduit.ai/u/treo)\
**Post date:** [March 24, 2020, 12:14pm UTC](https://community.konduit.ai/t/java-7-compatibility-issues/306/6 "2020-03-24T12:14:01Z")

</div>

Yes, please open an issue on Github about it. Currently we are debating if it is worth it to reintroduce the java 7 compatibility, as even [Red Hat is dropping support for OpenJDK7 in June](https://access.redhat.com/articles/1299013) and even android can handle class files compiled for java 8.