[JAVA] Command Pattern

Command Pattern Create a class to save the class instance (command.class) and treat the method of the saved class instance like the command.class method.

On this page -Simple Command pattern -Addition of a function to display the number of method executions I will describe about

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Simple Command pattern

It has the following configuration

class Explanation
command.interface Make the registered instance common
samCommand1.class Implement command and have one method
samCommand2.class Implement command and have one method
commandPool.class Save instances of samCommand1 and samCommand2
user(Main.class) Command.Check the operation of class
  • User Includes the meaning that other developers use this pattern


interface command{
  void s();


class samCommand1 implements command{
  public void s(){System.out.println("command1");}


class samCommand2 implements command{
  public void s(){System.out.println("command2");}


class commandPool{
  command[] pool=new command[2];  // command.Stores a class instance that implements interface
  void set(int key,command com){
  void exec(int key){


public static void main(String[] args){
  samCommand1 sc1 = new samCommand1();
  samCommand2 sc2 = new samCommand2();
  commandPool cop = new commandPool();

Addition of function to display method execution count

Modify commandPool.class to below


class commandPool{
  command[] pool = new command[4];
  int[] count = new int[2];
  void  set(int key,command com){
    if(pool [key]==null){
       pool [key]=com;
  void exec(int key){
    pool [key].s();

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