java design pattern - command pattern

这个command pattern 貌似用处还挺多的，而且也算是比教复杂的pattern 了，anyway ,直接上代码。

一个简单的代码如下：

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package CommandPattern;
//Command interface with an execute() method
interface Command{
public void execute();
}
//Lunch is a receiver
class Lunch{
public void makeLunch(){
System.out.println("Lunch is being made");
}
}
//LunchCommand implements Command, it contains a reference to Lunch,a receiver
// Its execute() method invokes the appropriate action on the receiver
class LunchCommand implements Command{
Lunch lunch;
public LunchCommand(Lunch lunch){
this.lunch = lunch;
}
@Override
public void execute(){
lunch.makeLunch();
}
}
//Dinner is also receiver
class Dinner{
public void makeDinner(){
System.out.println("Dinner is being made");
}
}
/* The DinnerCommand is similar to LunchCommand.
* it contains a reference to Dinner, a receiver.
* Its execute() method invokes the makeDinner() action of the Dinner object
*/
class DinnerCommand implements Command{
Dinner dinner;
public DinnerCommand(Dinner dinner){
this.dinner = dinner;
}
@Override
public void execute(){
dinner.makeDinner();
}
}
/* MealInvoker is the invoker class, it contains a reference to the Command
* to invoke . Its invoke() method calls the execute() method of the Command
*/
class MealInvoker{
Command command;
public MealInvoker(Command command){
this.command = command;
}
public void setCommand(Command command){
this.command = command;
}
public void invoke(){
command.execute();
}
}
public class CommandPatternDemo {
public static void main(String[] args){
Lunch lunch = new Lunch(); //receiver
Command lunchCommand = new LunchCommand(lunch); //concrete command
Dinner dinner = new Dinner();
Command dinnerCommand = new DinnerCommand(dinner); //concrete command
MealInvoker mi = new MealInvoker(lunchCommand); //invoker
mi.invoke();
mi.setCommand(dinnerCommand);
mi.invoke();
}
}

下面这个要稍微复杂些了
参考了这个代码： https://gist.github.com/cangelis/1442951#file-command-class-php-L36

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package CommandPattern;
interface MyCommand{
public void Execute();
public void unExecute();
}
class Calculator{
private int current;
public Calculator(int current){
this.current = current;
}
public void Action(String operator, int operand){
switch(operator){
case "+":
this.current += operand;
break;
case "-":
this.current -= operand;
break;
case "*":
this.current *= operand;
break;
case "/":
this.current /= operand;
break;
}
}
public int getCurrent(){
return this.current;
}
}
class concreteCommand implements MyCommand{
protected String operator ;
protected int operand;
protected int _lastnum;
Calculator cal;
public concreteCommand(String operator,int operand, Calculator cal,int _lastnum){
this.operand = operand;
this.operator = operator;
this.cal = cal;
this._lastnum = _lastnum;
}
public void Execute(){
cal.Action(operator, operand);
}
public void unExecute(){
cal.Action(Undo(operator), operand);
}
private String Undo(String operator){
switch(operator){
case "+": return "-" ;
case "-": return "+" ;
case "*": return "/" ;
case "/": return "*" ;
default:
System.out.println("wrong operand");
return null;
}
}
}
class CalInvoker {
MyCommand command;
public CalInvoker(MyCommand command){
this.command = command;
}
public void setInvoker(MyCommand command){
this.command = command;
}
public void Invoke(){
command.Execute();
}
public void unInvoke(){
command.unExecute();
}
}
public class CommandPatternDemo2 {
public static void main(String[] args){
Calculator ca = new Calculator(0);
MyCommand cm1 = new concreteCommand("+",5,ca,0);
CalInvoker ci = new CalInvoker(cm1);
ci.Invoke();
System.out.println(ca.getCurrent());
ci.unInvoke();
System.out.println(ca.getCurrent());
}
}

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java design pattern - command pattern