有效的Java-要保持单例保证，您必须声明所有实例字段都是瞬态的，并提供一个“ readResolve”方法。通过在此处声明瞬态场能实现什么？这是一个示例：

....
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public final class MySingleton implements Serializable{
 private int state;
 private MySingleton() { state =15; }
 private static final MySingleton INSTANCE = new MySingleton();
 public static MySingleton getInstance() { return INSTANCE; }
 public int getState(){return state;}
public void setState(int val){state=val;}
private Object readResolve() throws ObjectStreamException {
  return INSTANCE; 
 }
    public static void main(String[] args) {
        MySingleton  c = null;
        try {
            c=MySingleton.getInstance();
            c.setState(25);
            FileOutputStream fs = new FileOutputStream("testSer.ser");
            ObjectOutputStream os = new ObjectOutputStream(fs);
            os.writeObject(c);
            os.close();
        } catch (Exception e) {
            e.printStackTrace();
        }

        try {
            FileInputStream fis = new FileInputStream("testSer.ser");
            ObjectInputStream ois = new ObjectInputStream(fis);
            c = (MySingleton) ois.readObject();
            ois.close();
            System.out.println("after deser: contained data is " + c.getState());
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}

无论我是否将’state’变量声明为瞬态，我都会将c.getState（）gettign打印为25。我在这里缺少什么吗？