public static void printType(Type type, boolean isDefinition)
  {
  if (type instanceof Class)
  {
  Class<?> t = (Class<?>) type;
  System.out.print(t.getName());
  }
  else if (type instanceof TypeVariable)
  {
  TypeVariable<?> t = (TypeVariable<?>) type;
  System.out.print(t.getName());
  if (isDefinition)
  printTypes(t.getBounds(), " extends ", " & ", "", false);
  }
  else if (type instanceof WildcardType)
  {
  WildcardType t = (WildcardType) type;
  System.out.print("?");
  printTypes(t.getUpperBounds(), " extends ", " & ", "", false);
  printTypes(t.getLowerBounds(), " super ", " & ", "", false);
  }
  else if (type instanceof ParameterizedType)
  {
  ParameterizedType t = (ParameterizedType) type;
  Type owner = t.getOwnerType();
  if (owner != null)
  {
  printType(owner, false);
  System.out.print(".");
  }
  printType(t.getRawType(), false);
  printTypes(t.getActualTypeArguments(), "<", ", ", ">", false);
  }
  else if (type instanceof GenericArrayType)
  {
  GenericArrayType t = (GenericArrayType) type;
  System.out.print("");
  printType(t.getGenericComponentType(), isDefinition);
  System.out.print("[]");
  }

  }

这里
type instanceof WildcardType
type instanceof ParameterizedType
type instanceof TypeVariable
type instanceof GenericArrayType
分别代表什么

type是后面的子类

instanceof是Java的一个二元操作符，主要是用来测试它左边的对象是否是它右边的类的实例,如果是的话返回true
type instanceof WildcardType   -----------WildcardType对象是否是type类的
type instanceof ParameterizedType
type instanceof TypeVariable
type instanceof GenericArrayType

在你的程序中，根据真假来判断是判断执行那个if里的语句的