2024.12.12

abstract class AbstractCommand{

    public abstract int execute(int value);

    public abstract int undo();

    public abstract int redo();

}

 

class ConcreteCommand extends AbstractCommand{

    private Adder adder = new Adder();

    private int value;

 

    public int execute(int value) {

        this.value=value;

        return adder.add(value);

    }

 

    public int undo() {

        return adder.add(-value);

    }

 

    public int redo() {

        return adder.add(+value);

    }

}

 

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("执行运算，运算结果为：" + i);

    }

 

    public void undo() {

        int i = command.undo();

        System.out.println("执行撤销，运算结果为：" + i);

    }

 

    public void redo() {

        int i = command.redo();

        System.out.println("执行重复，运算结果为：" + i);

    }

}

 

class Adder {

    private int num=0;

 

    public int add(int value) {

        num+=value;

        return num;

    }

}

 

class Client {

    public static void main(String args[]) {

        CalculatorForm form = new CalculatorForm();

        ConcreteCommand command = new ConcreteCommand();

        form.setCommand(command);

 

        form.compute(10);

        form.redo();

        form.compute(5);

        form.compute(10);

        form.undo();

 

    }

}