16.命令模式

[实验任务一]：多次撤销和重复的命令模式

某系统需要提供一个命令集合（注：可以使用链表，栈等集合对象实现），用于存储一系列命令对象，并通过该命令集合实现多次undo()和redo()操作，可以使用加法运算来模拟实现。

类图

代码

java代码

package test16;

public abstract class AbstractCommand {

    public abstract int execute(int value);
    public abstract int undo();
    public abstract int redo();

}

package test16;

public class Adder {

    private int num = 0;

    public int add(int value){
        num += value;
        return num;
    }

}

package test16;

public class CalculatorForm {

    private AbstractCommand command;

    public void setCommand(AbstractCommand command){
        this.command = command;
    }

    public void compute(int value){
        int i = command.execute(value);
        System.out.println("execute compute success,The result is "+i);
    }

    public void undo(){
        int i = command.undo();
        if(i!=-1) {
            System.out.println("execute undo success,The result is " + i);
        }
    }

    public void redo(){
        int i = command.redo();
        if(i!=-1){
            System.out.println("execute redo success,The result is "+i);
        }

    }

}

package test16;

public class Client {

    public static void main(String[] args) {
        CalculatorForm form = new CalculatorForm();
        AbstractCommand command;
        command = new ConcreteCommand();

        form.setCommand(command);

        form.compute(10);
        form.compute(3);
        form.undo();
        form.undo();
        form.undo();
        form.redo();
        form.redo();
        form.redo();
    }

}

package test16;

import java.util.ArrayList;
import java.util.List;

public class ConcreteCommand extends AbstractCommand{

    /**
     * @apiNote This is my code
     * @date 2022.10.20
     */
    private Adder adder = new Adder();
    private int value;
    private List<Integer> undoValue = new ArrayList<>();
    private List<Integer> redoValue = new ArrayList<>();

    @Override
    public int execute(int value) {
        this.value = value;
        //The addition goes to the undo queue, which means the operation can be undone
        undoValue.add(value);
        return adder.add(value);
    }

    @Override
    public int undo() {
        if (undoValue.size()>0){
            int val = undoValue.get(undoValue.size()-1);
            undoValue.remove(undoValue.size()-1);
            //If added to the recovery group, recovery can be performed
            redoValue.add(val);
            return adder.add(-val);
        }else {
            System.out.println("It is't undo");
            return -1;
        }
    }

    @Override
    public int redo() {
        if(redoValue.size()>0){
            int val = redoValue.get(redoValue.size()-1);
            redoValue.remove(redoValue.size()-1);
            undoValue.add(val);
            return adder.add(val);
        }else {
            System.out.println("It is't redo");
            return -1;
        }

    }
}

C++代码

#include <iostream>
#include <list>
using namespace std;

class AbstractCommand{
public:
    virtual int execute(int value){};
    virtual int undo(){};
    virtual int redo(){};
};

class Adder{
private:
    int num = 0;
public:
    int add(int value) {
        num += value;
        return num;
    }
};

class CalculatorForm{
private:
    AbstractCommand* command;
public:
    void setCommand(AbstractCommand* command){
        this->command = command;
    }
    void compute(int value){
        int i = command->execute(value);
        cout<<"execute compute success,The result is ";
        cout<<i<<endl;
    }
    void undo(){
        int i = command->undo();
        if(i!=-1) {
            cout<<"execute undo success,The result is ";
            cout<<i<<endl;
        }
    }
    void redo(){
        int i = command->redo();
        if(i!=-1){
            cout<<"execute redo success,The result is ";
            cout<<i<<endl;
        }
    }
};

class ConcreteCommand: public AbstractCommand{
private:
    Adder adder;
    int value;
    list<int> undoValue;
    list<int> redoValue;
public:
    int execute(int value) {
        this->value = value;
        //The addition goes to the undo queue, which means the operation can be undone
        undoValue.push_back(value);
        return adder.add(value);
    }
    int undo() {
        if (undoValue.size()>0){
            int val = undoValue.back();
            undoValue.remove(undoValue.size()-1);
            //If added to the recovery group, recovery can be performed
            redoValue.push_back(val);
            return adder.add(-val);
        }else {
            cout<<"It is't undo"<<endl;
            return -1;
        }
    }
    int redo() {
        if(redoValue.size()>0){
            int val = redoValue.back();
            redoValue.remove(redoValue.size()-1);
            undoValue.push_back(val);
            return adder.add(val);
        }else {
            cout<<"It is't redo"<<endl;
            return -1;
        }

    }
};

int main(){

    CalculatorForm form;
    ConcreteCommand *command = new ConcreteCommand;
    form.setCommand(command);

    form.compute(10);
    form.compute(3);
    form.undo();
    form.undo();
    form.undo();
    form.redo();
    form.redo();
    form.redo();
}

原文地址：http://www.cnblogs.com/java-six/p/16861378.html