我有一个包含graph
和vertices
的edges
,并且我有一个originator
类,该类包含应用于graph
或insert vertices
在get the list of vertices
中的graph
界面vertex
public interface Vertex<V> {
public V element();
}
界面
edge
public interface Edge<E, V> {
public E element();
public Vertex<V>[] vertices();
}
接口
graph
与插入新顶点,其他方法是hide()public interface Graph<V, E> {
public void insertVertex(V vElement);
public Iterable<Vertex<V>> vertices();
}
ADT
Graph
实现,用于存储vertices
的集合(以及边,但不是必需的)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
}
}
类别
Memento
public class Memento {
private Graph graph;
public Memento(Originator originator) {
graph = originator.getGraph();
}
public Graph getGraph() {
return graph;
}
}
类别
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;
}
}
界面
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);
}
}
}
我的怀疑在保存状态后开始,并且尝试撤消
graph
不会更新为先前的状态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);
}
}
但是当我恢复de
graph
时仍然有2个顶点caretaker.restore(originator);
有什么建议吗?
最佳答案
您引用的是Memento内部相同的顶点集合。
尝试更改以下类:
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 Originator(Originator<V, E> originator) {
this.graph = new GraphEdgeList((GraphEdgeList) originator.getGraph());
this.caretaker = originator.getCaretaker();
}
public Memento createMemento() {//create new memento
return new Memento(new Originator(this));
}
public void setMemento(Memento memento) {//set memento
graph = memento.getGraph();
}
public Graph getGraph() {
return graph;
}
public Caretaker getCaretaker() {
return caretaker;
}
}
请参阅新的构造函数。
public class GraphEdgeList<V, E> implements Graph<V, E> {
private Map<V, Vertex<V>> vertices;
public GraphEdgeList() {
this.vertices = new HashMap<>();
}
public GraphEdgeList(GraphEdgeList graph) {
this.vertices = new HashMap<>();
this.vertices.putAll(graph.getVertices());
}
@Override
public void insertVertex(V vElement) {
this.vertices.put(vElement, null);
}
public Map<V, Vertex<V>> getVertices() {
return vertices;
}
public void setVertices(Map<V, Vertex<V>> vertices) {
this.vertices = vertices;
}
@Override
public Iterable<Vertex<V>> vertices() {
return this.vertices.values();
}
@Override
public String toString() {
return "GraphEdgeList [vertices=" + vertices + "]";
}
}
关于java - Memento无法在Java中使用undo更新状态,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/54514983/