Java设计模式之备忘录模式详解

// 发起人：文本编辑器
public class TextEditor {
    private String content;
    public void setContent(String content) {
        this.content = content;
    }
    public String getContent() {
        return content;
    }
    public TextEditorMemento save() {
        return new TextEditorMemento(content);
    }
    public void restore(TextEditorMemento memento) {
        this.content = memento.getContent();
    }
}
// 备忘录：文本编辑器的状态
public class TextEditorMemento {
    private String content;
    public TextEditorMemento(String content) {
        this.content = content;
    }
    public String getContent() {
        return content;
    }
}
// 负责人：文本编辑器的状态管理
public class TextEditorHistory {
    private Stack<TextEditorMemento> history = new Stack<>();
    public void save(TextEditorMemento memento) {
        history.push(memento);
    }
    public TextEditorMemento undo() {
        if (!history.isEmpty()) {
            return history.pop();
        }
        return null;
    }
}