Class中的方法原始碼：

public T cast(Object obj) {
     if (obj != null && !isInstance(obj))
          throw new ClassCastException(cannotCastMsg(obj));
     return (T) obj;
}

測試程式碼：

@Test
public void testCast() {
    Object worker = new Worker();
    //cast方法是就是將引數worker強制轉換為其對應的型別
    //以下兩種方法作用相同
 

    Worker worker1 = Worker.class.cast(worker);
    Worker worker2 = (Worker)worker;
    System.out.println(worker1.getCountry());
}