static S heapWalker_stringValue(Instance obj) {
  if (obj == null) null;
  
  if (!"java.lang.String".equals(obj.getJavaClass().getName()))
    throw new IllegalArgumentException("Is not a string: " + obj.getInstanceId() + " (" + obj.getJavaClass().getName() + ")");
    
  int UTF16 = 1;
  Bool COMPACT_STRINGS = cast obj.getJavaClass().getValueOfStaticField("COMPACT_STRINGS");
  if (COMPACT_STRINGS == null)
    ret HeapWalker.stringValue(obj); // We're pre Java 9
    
  O valueInstance = obj.getValueOfField("value");
  PrimitiveArrayInstance chars = cast valueInstance;
  
  byte coderField = cast obj.getValueOfField("coder");
  byte coder = COMPACT_STRINGS ? coderField : (byte) UTF16;
  int len = chars.getLength() >> coder;
  char[] text = new char[len];
  
  L<S> values = (L) chars.getValues();
  if (coder == UTF16)
    for (int i = 0; i < text.length; i++)
      text[i] = values.get(i).charAt(0);
  else
    for (int i = 0; i < text.length; i++)
      text[i] = (char) Int.parseInt(values.get(i));
 
  ret new String(text);
}