Javascript 实例字段本机JS全局

如何将实例字段转换为本地全局javascript变量，以便可以从javascript方法调用它

public class AA implements EntryPoint {

  public final int a =44;

}

public class AA implements EntryPoint {

  public final int a =44;

}

public native void init ( Integer arg )/*-{
    $wnd.a = arg;
}-*/;