11.26
命令模式
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package src;//抽象命令类 public abstract class AbstractCommand { public abstract int execute(int value); //声明命令执行方法execute() public abstract int undo(); //声明撤销方法undo() } |
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package src;//加法类：请求接收者 public class Adder { private int num=0; //定义初始值为0 //加法操作，每次将传入的值与num作加法运算，再将结果返回 public int add(int value) { num += value; return num; } } |
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package src;public class CalculatorForm { private AbstractCommand command; public void setCommand(AbstractCommand command) { this.command = command; } //调用命令对象的execute()方法执行运算 public void compute(int value) { int i = command.execute(value); System.out.println("执行结果为" + i); } //调用命令对象的undo()方法执行撤销 public void undo() { int i = command.undo(); System.out.println("撤销：" + i); } } |
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package src;public class Client { public static void main(String args[]) { CalculatorForm form = new CalculatorForm(); AbstractCommand command; command = new ConcreteCommand(); form.setCommand(command); //向发送者注入命令对象 form.compute(3); form.compute(4); form.compute(5); form.undo(); form.undo(); form.undo(); } } |
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package src;//具体命令类 class ConcreteCommand extends AbstractCommand { private Adder adder = new Adder(); private int value; //实现抽象命令类中声明的execute()方法，调用加法类的加法操作 public int execute(int value) { this.value=value; return adder.add(value); } //实现抽象命令类中声明的undo()方法，通过加一个相反数来实现加法的逆向操作 public int undo() { return adder.add(-value); } } |
