Method reference lambdas are not supported on IBM JDK

[giamma]

The IBM J9 JDK 8 does not have the private native method Class.getConstantPool().
Please note the J9 is the product name while the JDK level is Java 8.

When the static initialization is performed this results in a run-time error which is ignored in the catch block and the code probably assumes that this is the case because the JDK is < 8 and turns off boolean RESOLVES_LAMBDAS used to indicate whether lambdas are supported or not.

When later a lambda is to be processed a null is returned.

The only possible work around is to not use method references any more.

While version 8 of IBM JDK is only available via commercial subscription, later releases can be downloaded for free from the Adopt OpenJDK site under the name "Open J9".

[jhalterman]

Would be happy to take a PR for this.

[giamma]

Hi,

I did a bit of research, looking into the Oracle JDK and IBM JDK source code.

In IBM JDK >= 9 access to constant pool takes place in the exact same way as the Oracle JDK, meaning that the Class object provides the native method which returns the ConstantPool.

However, In IBM JDK 8 the java.lang package contains a package-visible class named Access, i.e. java.lang.Access which provides a method to get the constant pool given a class object:

final class Access  implements sun.misc.JavaLangAccess {
  // --- CUT ---
  public native sun.reflect.ConstantPool getConstantPool(Class<?> paramClass);
  // --- CUT ---
}

So to access the constant pool for a given class the following code could be used:
new java.lang.Access().getConstantPool( class );
(of course via reflection as Access is not accessible).

But even better, the Access class implements sun.misc.JavaLangAccess, and there is a factory method to instantiate it in class: sun.misc.SharedSecrets.getJavaLancAccess()
If you change your code to obtain the constant pool via JavaLangAccess and you first obtain the JavaLangAccess via sun.misc.SharedSecrets in JDK 8 and via jdk.internal.misc.SharedSecrets in JDK >= 9 then your code should be portable across all versions of both Oracle and IBM JDKs.

[jhalterman]

Thanks for digging into this. Care to submit a PR? :)

[giamma]

I don't have much time now, let's see.