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文章目录
  1. 备忘录模式

备忘录模式

  • 在不破坏封装性的前提下，捕获一个对象的内部状态，并在该对象之外保存这个状态。这样以后就可以将该对象恢复到原先保存的状态。
    Memento
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public class IterOriginator {
    private final Node root;
    private Node cursor = null;
    private Boolean isDone = false;
    private Stack<Node> stack;
    private Memento<Node> memento;
    public IterOriginator(Node root) {
        this.root = root;
        stack = new Stack<>();
        cursor = root;
        stack.push(cursor);
    }
    public Node next() {
        memento = createMemento();
        if (stack.isEmpty()) {
            isDone = true;
            return null;
        }
        Node top = stack.pop();
        cursor = top.right;
        if (cursor != null) {
            stack.push(cursor);
        }
        cursor = top.left;
        if (cursor != null) {
            stack.push(cursor);
        }
        return top;
    }
    public void undo() {
        setMemento(memento);
    }
    public Memento<Node> createMemento() {
        Memento<Node> memento = new Memento<>();
        Stack newStack=(Stack)stack.clone();
        memento.status = newStack;
        return memento;
    }
    public void setMemento(Memento<Node> memento) {
        this.stack = memento.status;
    }
}
public class Memento<T> {
    public Stack<T> status;
}
public class Node {
    public Node left;
    public Node right;
    public String name;
    public Node(Node left, Node right, String name) {
        this.left = left;
        this.right = right;
        this.name = name;
    }
    public Node(String name) {
        this.name = name;
    }
    public IterOriginator createFrontIndexIterator() {
        return new IterOriginator(this);
    }
}
public class App {
    public static void main(String[] args) {
        Node one = new Node(
                new Node(new Node(new Node("8"),null,"3"), new Node(new Node("6"), new Node("7"), "4"), "2"),
                new Node(new Node("9"),null,"5"), "1");
        IterOriginator iterOriginator=one.createFrontIndexIterator();
        Memento first=iterOriginator.createMemento();
        System.out.println(iterOriginator.next().name);
        System.out.println(iterOriginator.next().name);
        iterOriginator.setMemento(first);
        System.out.println(iterOriginator.next().name);
        System.out.println(iterOriginator.next().name);
    }
}
文章目录
  1. 备忘录模式