https://www.graalvm.org/ 
public final class com.oracle.truffle.js.runtime.builtins.JSWeakRefObject extends com.oracle.truffle.js.runtime.objects.JSNonProxyObject
  minor version: 0
  major version: 59
  flags: flags: (0x0031) ACC_PUBLIC, ACC_FINAL, ACC_SUPER
  this_class: com.oracle.truffle.js.runtime.builtins.JSWeakRefObject
  super_class: com.oracle.truffle.js.runtime.objects.JSNonProxyObject
{
  private final com.oracle.truffle.js.runtime.builtins.JSWeakRef$TruffleWeakReference<java.lang.Object> weakReference;
    descriptor: Lcom/oracle/truffle/js/runtime/builtins/JSWeakRef$TruffleWeakReference;
    flags: (0x0012) ACC_PRIVATE, ACC_FINAL
    Signature: Lcom/oracle/truffle/js/runtime/builtins/JSWeakRef$TruffleWeakReference<Ljava/lang/Object;>;

  protected void <init>(com.oracle.truffle.api.object.Shape, com.oracle.truffle.js.runtime.builtins.JSWeakRef$TruffleWeakReference<java.lang.Object>);
    descriptor: (Lcom/oracle/truffle/api/object/Shape;Lcom/oracle/truffle/js/runtime/builtins/JSWeakRef$TruffleWeakReference;)V
    flags: (0x0004) ACC_PROTECTED
    Code:
      stack=2, locals=3, args_size=3
        start local 0 // com.oracle.truffle.js.runtime.builtins.JSWeakRefObject this
        start local 1 // com.oracle.truffle.api.object.Shape shape
        start local 2 // com.oracle.truffle.js.runtime.builtins.JSWeakRef$TruffleWeakReference weakReference
         0: .line 51
            aload 0 /* this */
            aload 1 /* shape */
            invokespecial com.oracle.truffle.js.runtime.objects.JSNonProxyObject.<init>:(Lcom/oracle/truffle/api/object/Shape;)V
         1: .line 52
            aload 0 /* this */
            aload 2 /* weakReference */
            putfield com.oracle.truffle.js.runtime.builtins.JSWeakRefObject.weakReference:Lcom/oracle/truffle/js/runtime/builtins/JSWeakRef$TruffleWeakReference;
         2: .line 53
            return
        end local 2 // com.oracle.truffle.js.runtime.builtins.JSWeakRef$TruffleWeakReference weakReference
        end local 1 // com.oracle.truffle.api.object.Shape shape
        end local 0 // com.oracle.truffle.js.runtime.builtins.JSWeakRefObject this
      LocalVariableTable:
        Start  End  Slot           Name  Signature
            0    3     0           this  Lcom/oracle/truffle/js/runtime/builtins/JSWeakRefObject;
            0    3     1          shape  Lcom/oracle/truffle/api/object/Shape;
            0    3     2  weakReference  Lcom/oracle/truffle/js/runtime/builtins/JSWeakRef$TruffleWeakReference<Ljava/lang/Object;>;
    Signature: (Lcom/oracle/truffle/api/object/Shape;Lcom/oracle/truffle/js/runtime/builtins/JSWeakRef$TruffleWeakReference<Ljava/lang/Object;>;)V
    MethodParameters:
               Name  Flags
      shape          
      weakReference  

  public com.oracle.truffle.js.runtime.builtins.JSWeakRef$TruffleWeakReference<java.lang.Object> getWeakReference();
    descriptor: ()Lcom/oracle/truffle/js/runtime/builtins/JSWeakRef$TruffleWeakReference;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // com.oracle.truffle.js.runtime.builtins.JSWeakRefObject this
         0: .line 56
            aload 0 /* this */
            getfield com.oracle.truffle.js.runtime.builtins.JSWeakRefObject.weakReference:Lcom/oracle/truffle/js/runtime/builtins/JSWeakRef$TruffleWeakReference;
            areturn
        end local 0 // com.oracle.truffle.js.runtime.builtins.JSWeakRefObject this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lcom/oracle/truffle/js/runtime/builtins/JSWeakRefObject;
    Signature: ()Lcom/oracle/truffle/js/runtime/builtins/JSWeakRef$TruffleWeakReference<Ljava/lang/Object;>;
}
SourceFile: "JSWeakRefObject.java"
InnerClasses:
  public final TruffleWeakReference = com.oracle.truffle.js.runtime.builtins.JSWeakRef$TruffleWeakReference of com.oracle.truffle.js.runtime.builtins.JSWeakRef