Java中的设计模式Memento不使用undo更新状态
我有一个graph
包含vertices
和edges
,我还有一个originator
类,它包含graph
,应该用于insert vertices
或get the list of vertices
中的graph
接口vertex
public interface Vertex<V> {
public V element();
}
接口edge
public interface Edge<E, V> {
public E element();
public Vertex<V>[] vertices();
}
接口graph
插入一个新的顶点,其他方法是hide()
public interface Graph<V, E> {
public void insertVertex(V vElement);
public Iterable<Vertex<V>> vertices();
}
ADTGraph
实现,存储vertices
(和边,但不需要)的集合
public class GraphEdgeList<V, E> implements Graph<V, E> {
private Map<V, Vertex<V>> vertices;
public GraphEdgeList() {
this.vertices = new HashMap<>();
}
@Override
public void insertVertex(V vElement) {
//method to insert new vertex element
//not need to return nothing
}
@Override
public Iterable<Vertex<V>> vertices() {
//return a list of vertices in graph
}
}
类Memento
public class Memento {
private Graph graph;
public Memento(Originator originator) {
graph = originator.getGraph();
}
public Graph getGraph() {
return graph;
}
}
类Originator
public class Originator<V,E> {
private Graph<V,E> graph;
private Caretaker caretaker;
public Originator(Caretaker caretaker) {
this.graph = new GraphEdgeList();
this.caretaker = caretaker;
}
public Memento createMemento() {//create new memento
return new Memento(this);
}
public void setMemento(Memento memento) {//set memento
graph = memento.getGraph();
}
public Graph getGraph() {
return graph;
}
public Caretaker getCaretaker() {
return caretaker;
}
}
接口IMemento
public interface IMemento {
public void save(Originator originator);
public void restore(Originator originator);
}
类CareTaker
实现接口IMemento
public class Caretaker implements IMemento {
private final Stack<Memento> undoMemento;//stack explicit
public Caretaker() {
this.undoMemento = new StackDynamic();
}
@Override
public void save(Originator originator) {
Memento memento = originator.createMemento();
undoMemento.push(memento);
}
@Override
public void restore(Originator originator) {
if (undoMemento.isEmpty() != true) {
Memento memento = undoMemento.pop();
originator.setMemento(memento);
}
}
}
我的怀疑是在保存状态后开始的,当尝试执行撤消时,graph
不会更新到以前的状态
public class Main {
public static void main(String[] args) {
Caretaker caretaker = new Caretaker();
Originator<String, String> originator = new Originator(caretaker);
//create new string and insert in graph
originator.getGraph.insertVertex("A");
//caretaker save state
caretaker.save(originator);
//create another string and insert in graph
originator.getGraph.insertVertex("B");
//caretaker save state
caretaker.save(originator);
}
}
但是当我用两个顶点恢复degraph
caretaker.restore(originator);
有什么建议吗
# 1 楼答案
您正在引用Memento中的相同顶点集合
尝试更改以下类:
看看新的构造器