AddCommand
package SC16;

import java.util.Stack;

public class AddCommand extends Command{
    private Adder adder = new Adder();
    private Stack<Integer> unStack = new Stack<Integer>();// 撤回栈，用来记录所做的每一步操作，用于撤回
    private Stack<Integer> reStack = new Stack<Integer>();// 恢复栈，用来存储返回栈弹出的数据，用于恢复

    /**
     * 撤回
     */

    public int undo() {
        int i=0;
        if (unStack.isEmpty()) {
            i=-1;
        }else{
            Integer pop = unStack.pop();
            reStack.push(pop);   //将撤回栈中的栈顶元素弹出，并且压入恢复栈中
            if(!unStack.isEmpty()){//判断弹出数据后是否为空，如果为空，说明已撤回到最原始状态
                i=unStack.peek();
            }
        }
        return i;
    }

    /**
     * 恢复
     */
    public int redo() {
        int i=0;
        if (reStack.isEmpty()) {
            i=-1;
        }else{//撤回时只要可以可以撤回，则撤回栈一定有数据
            Integer pop = reStack.pop();
            unStack.push(pop);
            i=pop;
        }
        return i;
    }

    /**
     * 执行计算，并进行栈的更新
     */
    public int execute(int value) {
        int v = 0;
        v = adder.addOperate(value);
        System.out.println(v);
        unStack.push(v);
        return v;
    }
}

Adder
package SC16;

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

Client
package SC16;

public class Client {
    public static void main(String[] args) {
        Invoker inv = new Invoker();
        AddCommand command = new AddCommand();
        inv.setCommand(command);
        //计算
        System.out.println("计算过程:");
        inv.addNum(1);
        inv.addNum(2);
        inv.addNum(3);
        //多次撤回
        System.out.println("undo操作:");
        inv.undo();
        inv.undo();
        inv.undo();
        inv.undo();
        //多次恢复
        System.out.println("redo操作:");
        inv.redo();
        inv.redo();
        inv.redo();
        inv.redo();
    }
}

Command
package SC16;

public abstract class Command {
    public abstract int execute(int value);
    public abstract int undo();
    public abstract int redo();
}

Invoker
package SC16;

public class Invoker {
    private Command command;
    public void setCommand(Command command) {
        this.command =command;
    }
    /**
     * 执行运算
     * @param value
     */
    public void addNum(int value) {
        command.execute(value);
    }
    /**
     * 撤回
     */
    public void undo() {
        int i = command.undo();
        if(i==-1){
            System.out.println("已撤销到初态");
        }else{
            System.out.println("执行成功，运算结果是："+i);
        }
    }
    /**
     * 恢复
     */
    public void redo() {
        int i = command.redo();
        if(i==-1){
            System.out.println("已重复到终态");
        }
        else{
            System.out.println("执行成功，运算结果是："+i);
        }
    }
}