https://openjdk.java.net/ 
public interface org.graalvm.compiler.core.test.GraalCompilerTest$ArgSupplier extends java.util.function.Supplier<java.lang.Object>
  minor version: 0
  major version: 59
  flags: flags: (0x0601) ACC_PUBLIC, ACC_INTERFACE, ACC_ABSTRACT
  this_class: org.graalvm.compiler.core.test.GraalCompilerTest$ArgSupplier
  super_class: java.lang.Object
{
}
Signature: Ljava/lang/Object;Ljava/util/function/Supplier<Ljava/lang/Object;>;
SourceFile: "GraalCompilerTest.java"
NestHost: org.graalvm.compiler.core.test.GraalCompilerTest
InnerClasses:
  public abstract ArgSupplier = org.graalvm.compiler.core.test.GraalCompilerTest$ArgSupplier of org.graalvm.compiler.core.test.GraalCompilerTest
    RuntimeVisibleAnnotations: 
      java.lang.FunctionalInterface()