抽象和静态上下文中的java泛型

Question

我有抽象类A的不同子类，它们都应该实现getInstance方法。该方法检查实例是否已以xml格式（XStream library）保存在光盘上，并加载它或创建新实例

public MySubclassB extends A {   

...

private static SettingsManager<MySubclassB> manager;
private static MySubclassB instance;

private MySubclassB() {
    manager = new SettingsManager<MySubclassB>();
}

public static MySubclassB getInstance() {
    if (instance == null) {

        MySubclassB tmp = new MySubclassB();

        // loadObject returns either tmp if no instance was saved on disc or the saved object
        if ((instance = manager.loadObject(tmp, MySubclassB.class.getCanonicalName())).hashCode() == tmp.hashCode()) {
            setUpObjectFirstTime();
        } 
    }
    return instance;
}
}

是否可以在抽象类A中执行所有这些操作，或者我应该在所有子类中复制代码

Answer 1

您必须复制代码，因为类型参数仅与实例相关，因此不能在静态字段或方法中使用

https://docs.oracle.com/javase/tutorial/java/generics/restrictions.html#createStatic