Which Pattern is used in the following code? $($Tip: What happens in the application during the test run? See TestRun Class$)$

public interface Pos $\{$ void action$($CoCo c$,$ String n$)$; $\}$ public class Pos$1$ implements Pos $\{$ @Override public void action$($CoCo c$,$ String n$)\{$ System.out.println$($n $+"-"+1)$; c$.$me$($new Pos$2())$; $\}\}$ public class Pos$2$ implements Pos $\{$ @Override public void action$($CoCo c$,$ String n$)\{$ System.out.println$($n $+"-"+2)$; c$.$me$($new Pos$1())$; $\}\}$ public class CoCo $\{$ private Pos m; CoCo$()\{$ this.m$($new Pos$1())$; $\}$ void me$($Pos n$)\{$ m $=$ n; $\}$ public void exec$($String st$)\{$ m$.$action$($this$,$ st$)$; $\}\}$ public class TestRun $\{$ public static void main$($String$[]$ args$)\{$ CoCo sc $=$ new CoCo$()$; sc$.$exec$("$HelloWorld$")$; sc$.$exec$("$HelloWorld$")$; sc$.$exec$("$HelloWorld$")$; sc$.$exec$("$HelloWorld$")$; $\}\}$

Adapter Pattern

Decorator Pattern

Command Pattern

State Pattern

Proxy Pattern

Composite Pattern

Iterator Pattern

Template Pattern

Facade Pattern