https://www.graalvm.org/ 
final class com.oracle.truffle.nfi.NFIClosure implements com.oracle.truffle.api.interop.TruffleObject
  minor version: 0
  major version: 59
  flags: flags: (0x0030) ACC_FINAL, ACC_SUPER
  this_class: com.oracle.truffle.nfi.NFIClosure
  super_class: java.lang.Object
{
  final java.lang.Object executable;
    descriptor: Ljava/lang/Object;
    flags: (0x0010) ACC_FINAL

  final com.oracle.truffle.nfi.NFISignature signature;
    descriptor: Lcom/oracle/truffle/nfi/NFISignature;
    flags: (0x0010) ACC_FINAL

  void <init>(java.lang.Object, com.oracle.truffle.nfi.NFISignature);
    descriptor: (Ljava/lang/Object;Lcom/oracle/truffle/nfi/NFISignature;)V
    flags: (0x0000) 
    Code:
      stack=2, locals=3, args_size=3
        start local 0 // com.oracle.truffle.nfi.NFIClosure this
        start local 1 // java.lang.Object executable
        start local 2 // com.oracle.truffle.nfi.NFISignature signature
         0: .line 67
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
         1: .line 68
            aload 0 /* this */
            aload 1 /* executable */
            putfield com.oracle.truffle.nfi.NFIClosure.executable:Ljava/lang/Object;
         2: .line 69
            aload 0 /* this */
            aload 2 /* signature */
            putfield com.oracle.truffle.nfi.NFIClosure.signature:Lcom/oracle/truffle/nfi/NFISignature;
         3: .line 70
            return
        end local 2 // com.oracle.truffle.nfi.NFISignature signature
        end local 1 // java.lang.Object executable
        end local 0 // com.oracle.truffle.nfi.NFIClosure this
      LocalVariableTable:
        Start  End  Slot        Name  Signature
            0    4     0        this  Lcom/oracle/truffle/nfi/NFIClosure;
            0    4     1  executable  Ljava/lang/Object;
            0    4     2   signature  Lcom/oracle/truffle/nfi/NFISignature;
    MethodParameters:
            Name  Flags
      executable  
      signature   

  boolean isExecutable(com.oracle.truffle.api.interop.InteropLibrary);
    descriptor: (Lcom/oracle/truffle/api/interop/InteropLibrary;)Z
    flags: (0x0000) 
    Code:
      stack=2, locals=2, args_size=2
        start local 0 // com.oracle.truffle.nfi.NFIClosure this
        start local 1 // com.oracle.truffle.api.interop.InteropLibrary interop
         0: .line 74
            aload 1 /* interop */
            aload 0 /* this */
            getfield com.oracle.truffle.nfi.NFIClosure.executable:Ljava/lang/Object;
            invokevirtual com.oracle.truffle.api.interop.InteropLibrary.isExecutable:(Ljava/lang/Object;)Z
            ireturn
        end local 1 // com.oracle.truffle.api.interop.InteropLibrary interop
        end local 0 // com.oracle.truffle.nfi.NFIClosure this
      LocalVariableTable:
        Start  End  Slot     Name  Signature
            0    1     0     this  Lcom/oracle/truffle/nfi/NFIClosure;
            0    1     1  interop  Lcom/oracle/truffle/api/interop/InteropLibrary;
    RuntimeVisibleAnnotations: 
      com.oracle.truffle.api.library.ExportMessage()
    RuntimeInvisibleParameterAnnotations: 
      0:
        com.oracle.truffle.api.library.CachedLibrary(value = "this.executable")
    MethodParameters:
         Name  Flags
      interop  
}
SourceFile: "NFIClosure.java"
NestMembers:
  com.oracle.truffle.nfi.NFIClosure$Execute
InnerClasses:
  Execute = com.oracle.truffle.nfi.NFIClosure$Execute of com.oracle.truffle.nfi.NFIClosure
    RuntimeVisibleAnnotations: 
      com.oracle.truffle.api.library.ExportLibrary(value = Lcom/oracle/truffle/api/interop/InteropLibrary;)